David Stetson | The Ohio State University (original) (raw)
Papers by David Stetson
Journal of Experimental Zoology, 1978
... Kensler 1960 Factors which affect the activity of glutaminase I in the guinea-pig kidney. ...... more ... Kensler 1960 Factors which affect the activity of glutaminase I in the guinea-pig kidney. ... McBean, R. L., and L. Goldstein 1970 Renal function dur-ing osmotic stress in the ... Munro, AF 1953 Theammonia and urea excretion of different species of amphibia during development and ...
Kidney International, 1988
The American journal of physiology, 1983
The changes in cell structure produced during stimulation of proton secretion by CO2 in turtle bl... more The changes in cell structure produced during stimulation of proton secretion by CO2 in turtle bladder were examined using ultrastructural morphometric methods. One hour after CO2 addition, the area of the luminal membrane of the carbonic anhydrase-containing (CA) cell population was increased 2.5-fold and the volume percent of electron-lucent cytoplasmic vesicles in these CA cells was decreased by 61%. No changes were observed in the epithelial granular cells. These results suggest that during CO2 stimulation the vesicles fuse with the luminal membrane. CO2 stimulation of proton secretion is inhibited by the cytoskeleton-disrupting drugs colchicine and cytochalasin B and by 99% deuterium oxide as the Ringer solvent. Deuterium oxide also inhibits the decrease in cytoplasmic vesicles. Thus stimulation of proton secretion by turtle bladder CA cells depends to a large extent on vesicle fusion and the resultant increase in luminal surface area.
The American journal of physiology, 1991
In mammals, the length of the loops of Henle increases with increasing body size without a concom... more In mammals, the length of the loops of Henle increases with increasing body size without a concomitant rise in urinary concentrating ability. Because mass-specific metabolic rate falls with increasing body mass, this study sought to determine the extent to which this decline in metabolic rate could explain the low urinary concentrating ability of large mammals with long loops of Henle. Mitochondrial ultrastructural parameters were measured in the medullary thick ascending limbs (mTALs) of a series of nine mammalian genera ranging in body mass from 0.011 kg (bats) to approximately 400 kg (horses). The volume of mitochondria as a percent of mTAL cellular volume declined with increasing body mass (Mb-0.056). Inner mitochondrial membrane area per volume of mitochondrion also declined with increasing body mass (Mb-0.034), as did basolateral membrane area per unit mTAL cellular volume (Mb-0.075). Thus, not only do mitochondria occupy more volume of mTAL cells of smaller mammals, but those...
Turtle urinary bladder possesses four ion transport processes: Na+ absorption, H+ secretion, and ... more Turtle urinary bladder possesses four ion transport processes: Na+ absorption, H+ secretion, and HCO3- secretion-Cl- absorption. Each transport process is performed by a specific epithelial cell type. Granular cells absorb Na+ but they are not sensitive to antidiuretic hormone (ADH), unlike toad bladder granular cells. alpha-Carbonic anhydrase-rich (CA) cells secrete H+ via an apical H+-adenosinetriphosphatase (ATPase). Under conditions of low CO2 tension, this active pump is contained in the limiting membranes of certain cytoplasmic vesicles. The vesicles fuse with the apical membrane, and H+ pumps are incorporated into that membrane, as physiological conditions demand increased H+ secretion. The stimulus for fusion of these vesicles with the apical membrane appears to be intracellular acidification. beta-CA cells secrete HCO3- and reabsorb Cl-, both processes driven by H+-ATPase in the basolateral membrane in series with an apical Cl- -HCO3- exchanger. Increased intracellular adenosine 3',5'-cyclic monophosphate concentration in beta-cells stimulates net HCO3- secretion and induces an electrogenic component of this flux by activating an apical Cl- channel. This activation accompanies the fusion of an intracellular tubulovesicular network with the apical membrane. The membrane of this network may contain Cl- channels.
The American journal of physiology, 1984
The cellular ultrastructure of the renal distal nephron of the salamander, Amphiuma means, was ex... more The cellular ultrastructure of the renal distal nephron of the salamander, Amphiuma means, was examined by electron-microscopic and stereological techniques before and after exposure to potassium in the ambient environment. The distal nephron of Amphiuma is composed of three ultrastructurally distinct segments: early distal (or diluting segment), late distal, and collecting tubule. The early distal tubule structurally resembles the mammalian thick ascending limb of Henle's loop. Large renin-like granules are present in the smooth muscle cells of the afferent arteriole in the vicinity of the early distal tubule, suggesting the presence of a rudimentary juxtaglomerular apparatus. Late distal tubules are composed of one large cell type characterized by extensive basal membrane invaginations, often extending to the luminal membrane. Collecting tubules contain principal and intercalated cells that are ultrastructurally similar to cells of the mammalian cortical collecting tubule. Exp...
Journal of electron microscopy technique, 1989
Tissue and Cell, 1993
The ultrastructure of the ring gland (corpus cardiacum (CC), prothoracic gland (PG) and corpus al... more The ultrastructure of the ring gland (corpus cardiacum (CC), prothoracic gland (PG) and corpus allatum (CA)) was examined in diapausing and nondiapausing flesh fly pupae. The diapause developmental state, which is environmentally regulated and coordinated by the brain-ring gland complex, is associated with differences in the ultrastructure of PG and CA cells but not in the CC. During diapause the PG and CA cells have extensive arrays of rough endoplasmic reticulum and spherical mitochondria. The PG cells also contain lipid droplets surrounded by an electron dense amorphous coat not seen in PG cells from nondiapausing pupae. In nondiapausing pupae, the PG and CA cells contain large amounts of ribosomes throughout the cytoplasm but very little rough endoplasmic reticulum and elongated mitochondria. The fact that ring glands from diapausing pupae readily incorporate (35)S-methioninc indicates that the gland is actively synthesizing proteins, thus the contrasts in ring gland ultrastructure are not due to cellular quiescence during diapause but reflect fundamental cellular and physiological differences between the diapause and nondiapause developmental program.
Kidney International, 1980
Freeze-fracture and thin-section electron microscopy and morphometry were used to characterize fu... more Freeze-fracture and thin-section electron microscopy and morphometry were used to characterize further the response of the rat medullary collecting duct to potassium depletion. In freeze-fracture replicas, principal cells and intercalated cells were identified based on the assumption that intercalated cells possess a high density of rod-shaped intramembrane particles in their luminal membranes. Potassium depletion caused an increase in the relative number of cells with a high density of rod-shaped particles from the control level of 22% to 31% after 2 weeks and to 36% after 4 weeks. The frequency of intercalated cells identified by thin-section criteria was, however, about 35% in controls and unchanged by potassium depletion. This suggests that intercalated cells can have two types of membrane morphology. In potassium depletion, all intercalated cells display a high density of rod-shaped particles in their luminal membranes. In addition, the luminal membrane area of intercalated cells increased more than threefold, and the density of their rod-shaped particles increased by 21%. These observations suggest that the intercalated cell and its rod-shaped particle may be involved with the potassium reabsorption that occurs in this nephron segment with potassium depletion.
Journal of Morphology, 1990
A kidney from the budgerigar (budgie, parakeet; Melopsittacus undulatus) is composed of cortical ... more A kidney from the budgerigar (budgie, parakeet; Melopsittacus undulatus) is composed of cortical reptilian-type nephrons (without loops of Henle) and mammalian-type nephrons (with loops) grouped together in medullary cones. The loop of the mammalian-type nephrons has a descending segment composed of thin and highly interdigitated cells. These thin limb cells have few mitochondria (15% of cell volume), undetectable Na+,K(+)-ATPase activity, and virtually no basolateral surface amplification. Prior to the hairpin turn, the descending limb thickens, but the cells continue to lack basolateral amplification. Cells just prior to and within the hairpin turn resemble cells of the entire ascending limb. These cells are thick (there is no thin ascending segment in the avian loop), with extensive infoldings of the basolateral membrane surrounding numerous mitochondria (45% of cell volume). The area of basolateral membrane is 25 times that of the apical membrane. The basolateral membrane (but not the apical membrane) is enriched in Na+,K(+)-ATPase activity. The structure of the avian mammalian-type nephron (as epitomized by the budgie nephron) and the fact that NaCl accounts for over 90% of the osmotic activity of avian urine leads to the conclusion that the countercurrent multiplier of the avian kidney functions by active NaCl transport from the entire ascending limb. No explanation is offered for the transport specializations found in the thick descending segment of the loop, just prior to the hairpin turn.
The Journal of Membrane Biology, 1983
The polyene antibiotic filipin was used to characterize the cholesterol distribution in the membr... more The polyene antibiotic filipin was used to characterize the cholesterol distribution in the membranes of the toad bladder epithelium in freeze-fracture replicas. The apical membranes of granular and mitochondria-rich cells incorporate moderate amounts of filipin while the basolateral membranes of both cell types incorporate substantially greater amounts. Intracellular membranes, in general, take up very little filipin. The major exception to this is the granule membrane, which appears to be rich in cholesterol. An inverse correlation was found between the density of filipin-sterol complexes in the apical membrane and the incidence of granules in the cytoplasm. This suggests that fusion of granules with the apical membrane may be responsible for variation in the concentration of cholesterol in the apical membrane. Thirty minutes following vasopressin exposure, there is no consistent change in the cholesterol content of the apical membrane of granular cells as measured by the incidence of filipin-sterol complexes. The lack of change in the amount of membrane cholesterol indicates that the vasopressin-induced increase in transepithelial water permeability is not mediated by a change in cholesterol content of the apical membrane.
Journal of Insect Physiology, 1995
We examined the abilities of two Bacillus thuringiensis insecticidal toxins, CryIAa and CryIAc, p... more We examined the abilities of two Bacillus thuringiensis insecticidal toxins, CryIAa and CryIAc, prepared from Escherichia coli-cloned gene products, to inhibit short-circuit current in midgut epithelia of Bombyx mori. Voltage-clamp studies were conducted on isolated midguts, measuring the inhibition of short-circuit current (ISC) by trypsin-activated toxins. Three bathing solutions were compared and the medium of Chamberlin [(1990) J. exp. Biol.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1982
A technique for estimating effective transepithelial capacitance in vitro was used to investigate... more A technique for estimating effective transepithelial capacitance in vitro was used to investigate changes in epithelial cell membrane area in response to antidiuretic hormone (ADH) exposure in toad bladder. The results indicate that transepithelial capacitance increases by about 30% within 30 min after serosal ADH addition and decreases with ADH removal. This capacitance change is not blocked by amiloride and occurs whether or not there is a transepithelial osmotic gradient. It is blocked by methohexital, a drug which specifically inhibits the hydro-osmotic response of toad bladder to ADH. We conclude that the hydro-osmotic response of toad bladder to ADH is accompanied by addition of membrane to the plasmalemma of epithelial cells. This new membrane may contain channels that are permeable to water. Stimulation of Na+ transport by ADH is not related to membrane area changes, but appears to reflect activation of Na+ channels already present in the cell membrane before ADH challenge.
Annals of the New York Academy of Sciences, 1981
Page 1. ADH ACTION: EVIDENCE FOR A MEMBRANE SHUTTLE MECHANISM * James B. Wade, David L. Stetson,t... more Page 1. ADH ACTION: EVIDENCE FOR A MEMBRANE SHUTTLE MECHANISM * James B. Wade, David L. Stetson,t and Simon A. Lewis, Department of Physiology Yale University School of Medicine New Haven, Connecticut 06510 INTRODUCTION ...
Kidney International, 1988
The localization of carbonic anhydrase by histochemistry, of Na-K-ATPase by immunocytochemistry a... more The localization of carbonic anhydrase by histochemistry, of Na-K-ATPase by immunocytochemistry and of rod-shaped intramembranous particles by freeze-fracture electron microscopy, was determined in the collecting duct of rabbits. In the cortical collecting duct (CCD), rod-shaped particles, which are abundant in intercalated cells were observed in both the apical and basolateral membrane of all intercalated cells examined. In the outer stripe of the outer medullary collecting duct (OMCDo) a high density of rod-shaped particles was found only in the apical membrane of intercalated cells. All cells of the inner stripe of the outer medullary collecting duct (OMCDi) had rod-shaped particles in the apical membrane but not in the basolateral membrane. As the collecting duct entered the inner medulla the density of rod-shaped particles decreased until they were virtually absent in the terminal segment. Na-K-ATPase, localized to the basolateral membrane, was more abundant in principal cells than in intercalated cells in the CCD. In the OMCDo, staining was equal in principal and intercalated cells. All cells of the OMCDi and the inner medullary collecting duct (IMCD) stained for Na-K-ATPase. Carbonic anhydrase in the CCD was localized to the cell membranes and cytoplasm of intercalated cells. Principal cells did not stain for carbonic anhydrase. A similar pattern was seen in the OMCDo. In the outer region of the OMCDi most cells did not stain for carbonic anhydrase, whereas in the inner region the apical and lateral membranes of all cells stained for carbonic anhydrase. Weak cytoplasmic staining was occasionally seen. A similar pattern was seen in the initial half of the IMCD, while the terminal half of the IMCD did not stain. In this study, the localization of enzymes and rod-shaped intramembranous particles associated with Na+, K+, and H+ transport shows both segmental and cellular heterogeneity, and correlates with the known transport properties of tubule segments. The distribution of these enzymes and rod-shaped intramembranous particles is different in rabbits and rats, and may explain some of the functional differences between homologous segments in these species.
Journal of Experimental Zoology, 1978
... Kensler 1960 Factors which affect the activity of glutaminase I in the guinea-pig kidney. ...... more ... Kensler 1960 Factors which affect the activity of glutaminase I in the guinea-pig kidney. ... McBean, R. L., and L. Goldstein 1970 Renal function dur-ing osmotic stress in the ... Munro, AF 1953 Theammonia and urea excretion of different species of amphibia during development and ...
Kidney International, 1988
The American journal of physiology, 1983
The changes in cell structure produced during stimulation of proton secretion by CO2 in turtle bl... more The changes in cell structure produced during stimulation of proton secretion by CO2 in turtle bladder were examined using ultrastructural morphometric methods. One hour after CO2 addition, the area of the luminal membrane of the carbonic anhydrase-containing (CA) cell population was increased 2.5-fold and the volume percent of electron-lucent cytoplasmic vesicles in these CA cells was decreased by 61%. No changes were observed in the epithelial granular cells. These results suggest that during CO2 stimulation the vesicles fuse with the luminal membrane. CO2 stimulation of proton secretion is inhibited by the cytoskeleton-disrupting drugs colchicine and cytochalasin B and by 99% deuterium oxide as the Ringer solvent. Deuterium oxide also inhibits the decrease in cytoplasmic vesicles. Thus stimulation of proton secretion by turtle bladder CA cells depends to a large extent on vesicle fusion and the resultant increase in luminal surface area.
The American journal of physiology, 1991
In mammals, the length of the loops of Henle increases with increasing body size without a concom... more In mammals, the length of the loops of Henle increases with increasing body size without a concomitant rise in urinary concentrating ability. Because mass-specific metabolic rate falls with increasing body mass, this study sought to determine the extent to which this decline in metabolic rate could explain the low urinary concentrating ability of large mammals with long loops of Henle. Mitochondrial ultrastructural parameters were measured in the medullary thick ascending limbs (mTALs) of a series of nine mammalian genera ranging in body mass from 0.011 kg (bats) to approximately 400 kg (horses). The volume of mitochondria as a percent of mTAL cellular volume declined with increasing body mass (Mb-0.056). Inner mitochondrial membrane area per volume of mitochondrion also declined with increasing body mass (Mb-0.034), as did basolateral membrane area per unit mTAL cellular volume (Mb-0.075). Thus, not only do mitochondria occupy more volume of mTAL cells of smaller mammals, but those...
Turtle urinary bladder possesses four ion transport processes: Na+ absorption, H+ secretion, and ... more Turtle urinary bladder possesses four ion transport processes: Na+ absorption, H+ secretion, and HCO3- secretion-Cl- absorption. Each transport process is performed by a specific epithelial cell type. Granular cells absorb Na+ but they are not sensitive to antidiuretic hormone (ADH), unlike toad bladder granular cells. alpha-Carbonic anhydrase-rich (CA) cells secrete H+ via an apical H+-adenosinetriphosphatase (ATPase). Under conditions of low CO2 tension, this active pump is contained in the limiting membranes of certain cytoplasmic vesicles. The vesicles fuse with the apical membrane, and H+ pumps are incorporated into that membrane, as physiological conditions demand increased H+ secretion. The stimulus for fusion of these vesicles with the apical membrane appears to be intracellular acidification. beta-CA cells secrete HCO3- and reabsorb Cl-, both processes driven by H+-ATPase in the basolateral membrane in series with an apical Cl- -HCO3- exchanger. Increased intracellular adenosine 3',5'-cyclic monophosphate concentration in beta-cells stimulates net HCO3- secretion and induces an electrogenic component of this flux by activating an apical Cl- channel. This activation accompanies the fusion of an intracellular tubulovesicular network with the apical membrane. The membrane of this network may contain Cl- channels.
The American journal of physiology, 1984
The cellular ultrastructure of the renal distal nephron of the salamander, Amphiuma means, was ex... more The cellular ultrastructure of the renal distal nephron of the salamander, Amphiuma means, was examined by electron-microscopic and stereological techniques before and after exposure to potassium in the ambient environment. The distal nephron of Amphiuma is composed of three ultrastructurally distinct segments: early distal (or diluting segment), late distal, and collecting tubule. The early distal tubule structurally resembles the mammalian thick ascending limb of Henle's loop. Large renin-like granules are present in the smooth muscle cells of the afferent arteriole in the vicinity of the early distal tubule, suggesting the presence of a rudimentary juxtaglomerular apparatus. Late distal tubules are composed of one large cell type characterized by extensive basal membrane invaginations, often extending to the luminal membrane. Collecting tubules contain principal and intercalated cells that are ultrastructurally similar to cells of the mammalian cortical collecting tubule. Exp...
Journal of electron microscopy technique, 1989
Tissue and Cell, 1993
The ultrastructure of the ring gland (corpus cardiacum (CC), prothoracic gland (PG) and corpus al... more The ultrastructure of the ring gland (corpus cardiacum (CC), prothoracic gland (PG) and corpus allatum (CA)) was examined in diapausing and nondiapausing flesh fly pupae. The diapause developmental state, which is environmentally regulated and coordinated by the brain-ring gland complex, is associated with differences in the ultrastructure of PG and CA cells but not in the CC. During diapause the PG and CA cells have extensive arrays of rough endoplasmic reticulum and spherical mitochondria. The PG cells also contain lipid droplets surrounded by an electron dense amorphous coat not seen in PG cells from nondiapausing pupae. In nondiapausing pupae, the PG and CA cells contain large amounts of ribosomes throughout the cytoplasm but very little rough endoplasmic reticulum and elongated mitochondria. The fact that ring glands from diapausing pupae readily incorporate (35)S-methioninc indicates that the gland is actively synthesizing proteins, thus the contrasts in ring gland ultrastructure are not due to cellular quiescence during diapause but reflect fundamental cellular and physiological differences between the diapause and nondiapause developmental program.
Kidney International, 1980
Freeze-fracture and thin-section electron microscopy and morphometry were used to characterize fu... more Freeze-fracture and thin-section electron microscopy and morphometry were used to characterize further the response of the rat medullary collecting duct to potassium depletion. In freeze-fracture replicas, principal cells and intercalated cells were identified based on the assumption that intercalated cells possess a high density of rod-shaped intramembrane particles in their luminal membranes. Potassium depletion caused an increase in the relative number of cells with a high density of rod-shaped particles from the control level of 22% to 31% after 2 weeks and to 36% after 4 weeks. The frequency of intercalated cells identified by thin-section criteria was, however, about 35% in controls and unchanged by potassium depletion. This suggests that intercalated cells can have two types of membrane morphology. In potassium depletion, all intercalated cells display a high density of rod-shaped particles in their luminal membranes. In addition, the luminal membrane area of intercalated cells increased more than threefold, and the density of their rod-shaped particles increased by 21%. These observations suggest that the intercalated cell and its rod-shaped particle may be involved with the potassium reabsorption that occurs in this nephron segment with potassium depletion.
Journal of Morphology, 1990
A kidney from the budgerigar (budgie, parakeet; Melopsittacus undulatus) is composed of cortical ... more A kidney from the budgerigar (budgie, parakeet; Melopsittacus undulatus) is composed of cortical reptilian-type nephrons (without loops of Henle) and mammalian-type nephrons (with loops) grouped together in medullary cones. The loop of the mammalian-type nephrons has a descending segment composed of thin and highly interdigitated cells. These thin limb cells have few mitochondria (15% of cell volume), undetectable Na+,K(+)-ATPase activity, and virtually no basolateral surface amplification. Prior to the hairpin turn, the descending limb thickens, but the cells continue to lack basolateral amplification. Cells just prior to and within the hairpin turn resemble cells of the entire ascending limb. These cells are thick (there is no thin ascending segment in the avian loop), with extensive infoldings of the basolateral membrane surrounding numerous mitochondria (45% of cell volume). The area of basolateral membrane is 25 times that of the apical membrane. The basolateral membrane (but not the apical membrane) is enriched in Na+,K(+)-ATPase activity. The structure of the avian mammalian-type nephron (as epitomized by the budgie nephron) and the fact that NaCl accounts for over 90% of the osmotic activity of avian urine leads to the conclusion that the countercurrent multiplier of the avian kidney functions by active NaCl transport from the entire ascending limb. No explanation is offered for the transport specializations found in the thick descending segment of the loop, just prior to the hairpin turn.
The Journal of Membrane Biology, 1983
The polyene antibiotic filipin was used to characterize the cholesterol distribution in the membr... more The polyene antibiotic filipin was used to characterize the cholesterol distribution in the membranes of the toad bladder epithelium in freeze-fracture replicas. The apical membranes of granular and mitochondria-rich cells incorporate moderate amounts of filipin while the basolateral membranes of both cell types incorporate substantially greater amounts. Intracellular membranes, in general, take up very little filipin. The major exception to this is the granule membrane, which appears to be rich in cholesterol. An inverse correlation was found between the density of filipin-sterol complexes in the apical membrane and the incidence of granules in the cytoplasm. This suggests that fusion of granules with the apical membrane may be responsible for variation in the concentration of cholesterol in the apical membrane. Thirty minutes following vasopressin exposure, there is no consistent change in the cholesterol content of the apical membrane of granular cells as measured by the incidence of filipin-sterol complexes. The lack of change in the amount of membrane cholesterol indicates that the vasopressin-induced increase in transepithelial water permeability is not mediated by a change in cholesterol content of the apical membrane.
Journal of Insect Physiology, 1995
We examined the abilities of two Bacillus thuringiensis insecticidal toxins, CryIAa and CryIAc, p... more We examined the abilities of two Bacillus thuringiensis insecticidal toxins, CryIAa and CryIAc, prepared from Escherichia coli-cloned gene products, to inhibit short-circuit current in midgut epithelia of Bombyx mori. Voltage-clamp studies were conducted on isolated midguts, measuring the inhibition of short-circuit current (ISC) by trypsin-activated toxins. Three bathing solutions were compared and the medium of Chamberlin [(1990) J. exp. Biol.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1982
A technique for estimating effective transepithelial capacitance in vitro was used to investigate... more A technique for estimating effective transepithelial capacitance in vitro was used to investigate changes in epithelial cell membrane area in response to antidiuretic hormone (ADH) exposure in toad bladder. The results indicate that transepithelial capacitance increases by about 30% within 30 min after serosal ADH addition and decreases with ADH removal. This capacitance change is not blocked by amiloride and occurs whether or not there is a transepithelial osmotic gradient. It is blocked by methohexital, a drug which specifically inhibits the hydro-osmotic response of toad bladder to ADH. We conclude that the hydro-osmotic response of toad bladder to ADH is accompanied by addition of membrane to the plasmalemma of epithelial cells. This new membrane may contain channels that are permeable to water. Stimulation of Na+ transport by ADH is not related to membrane area changes, but appears to reflect activation of Na+ channels already present in the cell membrane before ADH challenge.
Annals of the New York Academy of Sciences, 1981
Page 1. ADH ACTION: EVIDENCE FOR A MEMBRANE SHUTTLE MECHANISM * James B. Wade, David L. Stetson,t... more Page 1. ADH ACTION: EVIDENCE FOR A MEMBRANE SHUTTLE MECHANISM * James B. Wade, David L. Stetson,t and Simon A. Lewis, Department of Physiology Yale University School of Medicine New Haven, Connecticut 06510 INTRODUCTION ...
Kidney International, 1988
The localization of carbonic anhydrase by histochemistry, of Na-K-ATPase by immunocytochemistry a... more The localization of carbonic anhydrase by histochemistry, of Na-K-ATPase by immunocytochemistry and of rod-shaped intramembranous particles by freeze-fracture electron microscopy, was determined in the collecting duct of rabbits. In the cortical collecting duct (CCD), rod-shaped particles, which are abundant in intercalated cells were observed in both the apical and basolateral membrane of all intercalated cells examined. In the outer stripe of the outer medullary collecting duct (OMCDo) a high density of rod-shaped particles was found only in the apical membrane of intercalated cells. All cells of the inner stripe of the outer medullary collecting duct (OMCDi) had rod-shaped particles in the apical membrane but not in the basolateral membrane. As the collecting duct entered the inner medulla the density of rod-shaped particles decreased until they were virtually absent in the terminal segment. Na-K-ATPase, localized to the basolateral membrane, was more abundant in principal cells than in intercalated cells in the CCD. In the OMCDo, staining was equal in principal and intercalated cells. All cells of the OMCDi and the inner medullary collecting duct (IMCD) stained for Na-K-ATPase. Carbonic anhydrase in the CCD was localized to the cell membranes and cytoplasm of intercalated cells. Principal cells did not stain for carbonic anhydrase. A similar pattern was seen in the OMCDo. In the outer region of the OMCDi most cells did not stain for carbonic anhydrase, whereas in the inner region the apical and lateral membranes of all cells stained for carbonic anhydrase. Weak cytoplasmic staining was occasionally seen. A similar pattern was seen in the initial half of the IMCD, while the terminal half of the IMCD did not stain. In this study, the localization of enzymes and rod-shaped intramembranous particles associated with Na+, K+, and H+ transport shows both segmental and cellular heterogeneity, and correlates with the known transport properties of tubule segments. The distribution of these enzymes and rod-shaped intramembranous particles is different in rabbits and rats, and may explain some of the functional differences between homologous segments in these species.