Multi-Responsiveness of Single Anterior Pituitary Cells to Hypothalamic-Releasing Hormones: A Cellular Basis for Paradoxical Secretion (original) (raw)
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Comparison of patterns of prolactin release in GH4C1 cells and primary pituitary cultures
Molecular and Cellular Endocrinology, 1985
The effects of 12-O-tetradecanoylphorbol-13-acetate (TPA, an activator of C-kinase), the cation ionophore A23187, forskolin (an activator of adenylate cyclase) and thyrotropin-releasing hormone (TRH) on prolactin release from anterior pituitary cells in primary culture were investigated and compared to the effects of these same agents on prolactin release from GH4C, cells. In both GH,C, cells and primary pituitary cultures, 100 nM TRH increased prolactin release 3-to 5-fold within 4 min after the stimulation started. This peak response was followed by a fall to a sustained increased rate of release approximately 1.5-fold above the basal rate. The decline after the early peak was slower in primary cultures than in GH,C, cells. Addition of 20 PM A23187 to primary cultures caused a rapid 2-to 4-fold increase in release that fell to basal values within 12 min after the stimulation started. In GH4C, cells, A23187 caused a rise in prolactin release of less than 2-fold that was sustained longer than the rise seen in primary cultures. Perifusion of either type of cells with 50 nM TPA caused a rapid 2-to 2.5-fold increase in release that also was sustained for 30 min or more in both types of cells. Perifusion with combined TPA and A23187 caused a 3-to 5-fold increase in rate of release from each cell type that declined rapidly to a 2-fold sustained release in primary cultures, and that declined more slowly in GH,C, cells. Forskolin, 1 PM, had only a small effect by itself, but potentiated the effect of TPA or combined TPA and A23187 in both types of cells. Forskolin did not potentiate the effect of TRH in primary cultures. Although there are differences in responses of the 2 types of cells, the overall patterns of response were similar. The data are consistent with a model in which 2 parts of the Ca2' messenger system participate in the action of TRH: an increase in cytosolic Ca2 + and an activation of protein kinase C. GH,C, cells are a subclone of the rat pituitary cell strain GH,, which was adapted to culture from a pituitary tumor (Tashjian et al., 1968). GH&, and GH, cells have been used extensively * A recipient of Research Career Development Award HD-00272. To whom all correspondence should be addressed.
Journal of Biological Chemistry, 1984
ylene glycol bis(8-aminoethyl ether)-N,N,N',N'-tetraacetic acid; AM, acetoxymethyl ester; Hepes, 4-(2-hydroxyethyl)-l-piperazineethanesulfonic acid; [ X ] , cytosolic free concentration of X; x, wavelength; t l / z , half-life; EDm, dose which gives 50% of maximum effect; KO, equilibrium dissociation constant; [X]., extracellular concentrations of X ; [X],, concentration of X at time t.
Anterior pituitary thyrotropes are multifunctional cells
American Journal of Physiology-endocrinology and Metabolism, 2004
Anterior pituitary (AP) contains some unorthodox multifunctional cells that store and secrete two different AP hormones (polyhormonal cells) and/or respond to several hypothalamic releasing hormones (HRHs) (multiresponsive cells). Multifunctional cells may be involved in paradoxical secretion (secretion of a given AP hormone evoked by a non-corresponding HRH) and trans-differentiation (phenotypic switch between different mature cell types without cell division). Here we combine calcium imaging (to assess responses to the four HRHs) and multiple sequential immunoassay of the six AP hormones to perform a single-cell phenotypic study of thyrotropes in normal male and female mice. Surprisingly, most of the thyrotropes were polyhormonal, containing, in addition to TSH, LH (40-42%) and prolactin (19-21%).
Hormone Secretion by Cells Dissociated from Rat Anterior Pituitaries
The Journal of Cell Biology, 1973
A new procedure has been developed for dissociating anterior pituitary tissue and producing a viable suspension of single cells. The procedure involves incubation of small tissue blocks in 1 mg/ml trypsin (15 min), followed by incubation in 8 µg/ml neuraminidase and 1 mM EDTA (15 min), followed by mechanical dispersion. Cell yields are ∼55%, based on recovered DNA. By electron microscopy five types of secretory cells (somatotrophs, mammotrophs, thyrotrophs, gonadotrophs, and corticotrophs) plus endothelial and follicular cells can be identified and are morphologically well preserved up to 20 h after dissociation. Throughout this period, the cells incorporate linearly [3H]leucine into protein for up to 4 h at a rate 90% greater than hemipituitaries, and they synthesize, transport intracellularly, and release the two major pituitary secretory products, growth hormone and prolactin. Immediately after dissociation the cells' ability to respond to secretogogues (high K+ and dibutyryl...
Immunocytochemistry of a ?private? luteinizing-hormone-releasing hormone system in the pituitary
Cell and Tissue Research, 1984
Immunocytochemistry of paraffin sections of Bouin-fixed rat pituitaries with antiserum to luteinizinghormone-releasing hormone (LHRH) revealed two types of cells. Type I cells exhibit granular staining throughout their cytoplasm. The immunoreactivity of type II cells is confined to a much smaller area of the cytoplasm. Type I cells are located in the ventral margin of the pars intermedia, the region between the pars intermedia and the pars distalis, and the pars distalis adjacent to this region. Type II cells have a broader distribution in the pars distalis, but tend to concentrate in the region of the pars distalis near the pars intermedia. Type I cells are distinct from gonadotropes. Type II cells appear to comprise a subgroup of gonadotropes. Staining in type I, but not type II, ceils in pituitary explants, maintained in serum-free media for seven days, is as intense as that in normal pituitary tissue. The data suggest that the type I cells are producing an intrinsic LHRH-like material and may be responsible, in part, for the regulation of some gonadotropes.
The Journal of Cell …, 1980
The secretion of prolactin in cultured pituitary cells was studied in correlation with the cellular changes induced by stimulatory or inhibitory agents. The techniques used in this study were : radioimmunoassay, immunocytochemistry, scanning (SEM) as well as transmission (TEM) electron microscopy. Prolactin secretion was stimulated by 17,8-estradiol (10 nM) as well as thyrotropin-releasing hormone (TRH) (3 nM) and inhibted by 2-Bra -ergocryptine (CB-154) (1 ftM). The total prolactin (release and cell content) increased between 2 and 8 d of estradiol treatment, indicating an increase of both synthesis and release of prolactin. This finding was in agreement with TEM observations because, in estradiol-treated prolactin cells, the Golgi saccules were distended and Golgi elements were increased, thus indicating increased synthetic activity of these cells. The addition of TRH over a 4-h period resulted in a significant degranulation of prolactin cells. In contrast, prolactin secretory granules became accumulated in the cells after CB-154 treatment for a period ranging from 4 to 24 h. In agreement, light microscope immunocytochemistry showed an increased reaction for prolactin after short-term (<24 h) incubation with CB-154. Because prolactin cells represent-70% of the glandular cell population as revealed by immunocytochemistry, it was then possible to observe the changes of cell surface by SEM. In most cells, estradiol and TRH led to an increase in the number and prominence of microvilli and blebs, whereas CB-154 treatment resulted in a slightly decreased number of microvilli and an increased occurrence of membrane foldings. This report thus provides morphological evidence for the stimulatory effects of estradiol and TRH, and the inhibitory effects of CB-154 on prolactin secretion in pituitary cells in primary culture. These data, moreover, show that acute changes in secretory activity of prolactin-secreting cells are accompanied by marked changes of their morphological characteristics. The secretion of prolactin in the anterior pituitary gland is under predominant inhibitory control by the hypothalamus (30). Recent data indicate that dopamine may be the main or even the only inhibitory substance of hypothalamic origin involved in the control of prolactin secretion (11, 29, 37). This role of dopamine is also supported by the finding that 2-bromoa-ergocryptine (CB-154), a potent dopamine agonist, and other
Molecular and cellular endocrinology, 1981
We have carried out further in vitro studies on the priming effect of LH-RH and the effect of steroids on pituitary responsiveness to LH-RH. In hemipituitary glands, the priming effect could be elicited only once within an 11-h period and was found to diminish significantly with time after the first exposure to LH-RH. Incubation with oestradiol-17 beta (E2) had no significant effect on the responsiveness of hemipituitary glands to LH-RH. By contrast, E2 increased the responsiveness of dispersed cell system. The presence of hypothalamus or synthetic LH-RH did not facilitate the effects of E2. Testosterone significantly reduced the spontaneous and LH-RH-induced release of LH while progesterone had no effect. Exposure to E2 alone in either of the systems did not produce a consistent increase in the total amount of LH in the system. Synthesis of LH was, however, stimulated by exposure to LH-RH for 48 h but not 12 h. These results demonstrate that there is a marked difference between the...
The Journal of cell biology, 1977
A derivative of the hypothalamic peptide luteinizing hormone-releasing hormone (LHRH) has been coupled to ferritin and the conjugate purified by gel chromatography. In its ability to stimulate the secretion of luteinizing hormone from pituitary cells in vitro, the conjugate has the same potency and specificity as the native peptide. When dissociated pituitary cells maintained in short-term culture are lightly fixed with formaldehyde and then incubated with the conjugate, examination in the electron microscope shows an even distribution of ferritin particles over the free cell surface of the gonadotrophin cells. This binding appears to be specific for the LHRH receptor since it is prevented by a 10-fold excess of native peptide. In addition to the gonadotrophin cells, some somatotrophin and thyrotrophin cells bind conjugate on their free surfaces under similar conditions. If living cells are incubated with the conjugate for 15 min, the bound conjugate becomes aggregated and then conc...