Iain L Buxton - Academia.edu (original) (raw)

Papers by Iain L Buxton

C. LONGHURST. Increased myocardial P-receptors and adrener-gic responses in hyperthyroid pigs. Am... more C. LONGHURST. Increased myocardial P-receptors and adrener-gic responses in hyperthyroid pigs. Am. J. Physiol. 252 (Heart Circ. Physiol. 21): H283-H290,1987.-Controversy exists pres-ently as to whether thyroid hormone potentiates the action of catecholamines on the heart. Therefore, the relationships be-tween adrenergic sensitivity, myocardial P-receptor number, and the cardiovascular responses associated with excess thyroid hormone were investigated in pigs (Sus scrofa). A hyperthyroid state was induced by the administration of triiodothyronine (T3; 1 mg/kg iv). After 7 days there was a significant increase in resting heart rate, systolic blood pressure, rate-pressure product, and O2 consumption in the hyperthyroid state. At this time echocardiography showed a substantial increase in myo-cardial cross-sectional size. Pharmacological tests showed an increased intrinsic heart rate (127 t 29 to 205 t 25 beats/min;

American Journal of Physiology-Heart and Circulatory Physiology, 2001

The Nucleotide Axis Hypothesis, defined and supported herein, proposes that ATP stimulates the re... more The Nucleotide Axis Hypothesis, defined and supported herein, proposes that ATP stimulates the release of vasoactive mediators from endothelium, including ATP itself. Here, we show rapid endothelium-dependent, agonist-stimulated ATP elaboration in coronary vessels of guinea pigs. Measurement of extracellular ADP metabolism in intact vessels results in the time- and substrate-dependent formation of ATP in the coronary perfusate in amounts greater than can be accounted for by release from endothelium alone. ATP formation by endothelial cells is saturable ( K M = 38.5 μmol/l, where K M is substrate concentration at which rate is half-maximal.) and trypsin-sensitive, membranes from [γ-32P]ATP-labeled cells support ADP-dependent transphosphorylation by a 20-kDa protein, Western blots reveal the presence of a nucleoside diphosphate kinase (NDPK) of ∼20 kDa in endothelial membranes, and analysis of NDPK antibody binding by flow cytometry is consistent with the presence of an ecto-NDPK on c...

PLoS ONE, 2010

Background: We tested the hypothesis that the stretch-activated, four-transmembrane domain, two p... more Background: We tested the hypothesis that the stretch-activated, four-transmembrane domain, two pore potassium channels (K2P), TREK-1 and TRAAK are gestationally-regulated in human myometrium and contribute to uterine relaxation during pregnancy until labor. Methodology: We determined the gene and protein expression of K2P channels in non-pregnant, pregnant term and preterm laboring myometrium. We employed both molecular biological and functional studies of K2P channels in myometrial samples taken from women undergoing cesarean delivery of a fetus.

Circulation Research, 1985

beta 1- and beta 2-Adrenergic receptors co-exist in the adult rat ventricle. We have employed rad... more beta 1- and beta 2-Adrenergic receptors co-exist in the adult rat ventricle. We have employed radioligand binding and cell purification techniques to determine the cellular origin of these receptors. The beta-adrenergic antagonist ligand (+/-)-[125I] iodocyanopindolol binds to 2 X 10(5) receptors per purified adult rat cardiomyocyte, with a dissociation constant of 70 pM. The subtype-selective antagonists betaxolol (beta 1), practolol (beta 1), and zinterol (beta 2) compete for [125I]iodocyanopindolol-binding sites on intact myocytes in monophasic manners with dissociation constants of 46, 845, and 923 nM, respectively. [125I]iodocyanopindolol binding to membranes prepared from nonmyocyte elements of rat ventricle occurs with a dissociation constant of 43 pM and a capacity of 88 fmol/mg membrane protein. Computer analysis of competition of [125I]iodocyanopindolol binding by betaxolol, practolol, and zinterol in nonmyocyte membranes demonstrates biphasic curves that comprise binding ...

Cellular Signalling, 1989

British Journal of Pharmacology, 1993

We have previously demonstrated that activation of M3 muscarinic receptors increases inositol 1,4... more We have previously demonstrated that activation of M3 muscarinic receptors increases inositol 1,4,5-trisphosphate (InsP3) and inositol 1,3,4,5-tetrakisphosphate (InsP4) accumulation in colonic smooth muscle. 2 In the present study, we demonstrate the existence of InsP3 and InsP4 binding sites in colonic circular smooth muscle by use of radioligand binding methods. Both [3H]-InsP3 and [3H]-InsP4 bound rapidly and reversibly to a single class of saturable sites in detergent-solubilized colonic membranes with affinities of 5.04 ± 1.03 nM and 3.41 ± 0.78 nM, respectively. The density of [3H]-InsP3 binding sites was 335.3 19.3 fmol mg-' protein which was approximately 2.5 fold greater than that of [3H]-InsP4 sites (127.3 ± 9.1 fmol mg-' protein). 3 The two high affinity inositol phosphate binding sites exhibited markedly different pH optima for binding of each radioligand. At pH 9.0, specific [3H]-InsP3 binding was maximal, whereas [3H]-InsP4 binding was only 10% that of [3H]-InsP3. Conversely, at pH 5.0, [3H]-InsP4 binding was maximal, while [3H]-InsP3 binding was reduced to 15% of its binding at pH 9.0. 4 InsP3 was about 20 fold less potent (K, = 50.7 ± 8.3 nM) than InsP4 in competing for [3H]-InsP4 binding sites and could compete for only 60% of [3H]-InsP4 specific binding. InsP4 was also capable of high affinity competition with [3H]-InsP3 binding (K1 = 103.5 ± 1.5 nM), and could compete for 100% of [3H]-InsP3 specific binding. 5 [3H]-InsP3 binding in subcellular fractions separated by discontinuous sucrose density gradients followed NADPH-cytochrome c reductase activity, suggesting an intracellular localization for the majority of InsP3 receptors in this tissue, whereas [3H]-InsP4 binding appeared to be equally distributed between plasma membrane and intracellular membrane populations. 6 These results suggest the existence of distinct and specific InsP3 and InsP4 binding sites which may represent the physiological receptors for these second messengers; differences in the subcellular distribution of these receptors may contribute to differences in their putative physiological roles.

Annals of the New York Academy of Sciences, 1990

Analytical Biochemistry, 1984

Using glycerol kinase and [3H]glycerol, a kinetic isotope dilution assay for glycerol has been de... more Using glycerol kinase and [3H]glycerol, a kinetic isotope dilution assay for glycerol has been developed. Reactant and product are separated by stepwise elution from QAE-Sephadex. This assay is sensitive to as little as 100 pmol of glycerol, avoids numerous drawbacks of the traditional fluorescent assay, and readily detects glycerol production by fewer than 10(5) cardiomyocytes.

Proceedings of the Western Pharmacology Society, 2003

Endothelial cells (EC) are known to express an ectonucleoside diphosphate kinase (eNDPK) thought ... more Endothelial cells (EC) are known to express an ectonucleoside diphosphate kinase (eNDPK) thought to participate in the moment-to-moment regulation of blood flow by maintaining the extracellular presence of nucleotides in the blood stream [1]. EC release of ATP following increases in shear stress or activation by hormones such as bradykinin (BK) signals nitric oxide (NO) release and this effect is propagated by ATP acting at purinergic receptors (P2y) on adjacent endothelium. The process of ATP release and its subsequent action at P2 receptors to stimulate further ATP release and metabolism constitutes a Nucleotide Axis in the blood vessel. We have proposed that this axis is a primary mechanism that maintains antithrombogenic and vasodilatory actions of ECs, since release of ATP in the blood vessel lumen can be expected to prevent platelet aggregation and stimulate endothelial P2y receptors coupled to release of NO and more ATP. While ATP-induced ATP release can serve to propagate th...

Annals of Pharmacotherapy, 2004

Scientific reports, Jan 4, 2018

Tocolytics show limited efficacy to prevent preterm delivery. In uterine smooth muscle cGMP accum... more Tocolytics show limited efficacy to prevent preterm delivery. In uterine smooth muscle cGMP accumulation following addition of nitric oxide (NO) has little effect on relaxation suggesting a role for protein S-nitrosation. In human myometrial tissues from women in labor at term (TL), or spontaneously in labor preterm (sPTL), direct stimulation of soluble guanylyl cyclase (sGC) fails to relax myometrium, while the same treatment relaxes vascular smooth muscle completely. Unlike term myometrium, effects of NO are not only blunted in sPTL, but global protein S-nitrosation is also diminished, suggesting a dysfunctional response to NO-mediated protein S-nitrosation. Examination of the enzymatic regulator of endogenous S-nitrosoglutathione availability, S-nitrosoglutathione reductase, reveals increased expression of the reductase in preterm myometrium associated with decreased total protein S-nitrosation. Blockade of S-nitrosoglutathione reductase relaxes sPTL tissue. Addition of NO donor ...

Translational Andrology and Urology

Critical reviews in biochemistry and molecular biology, 2017

S-nitrosoglutathione reductase (GSNOR), or ADH5, is an enzyme in the alcohol dehydrogenase (ADH) ... more S-nitrosoglutathione reductase (GSNOR), or ADH5, is an enzyme in the alcohol dehydrogenase (ADH) family. It is unique when compared to other ADH enzymes in that primary short-chain alcohols are not its principle substrate. GSNOR metabolizes S-nitrosoglutathione (GSNO), S-hydroxymethylglutathione (the spontaneous adduct of formaldehyde and glutathione), and some alcohols. GSNOR modulates reactive nitric oxide (•NO) availability in the cell by catalyzing the breakdown of GSNO, and indirectly regulates S-nitrosothiols (RSNOs) through GSNO-mediated protein S-nitrosation. The dysregulation of GSNOR can significantly alter cellular homeostasis, leading to disease. GSNOR plays an important regulatory role in smooth muscle relaxation, immune function, inflammation, neuronal development and cancer progression, among many other processes. In recent years, the therapeutic inhibition of GSNOR has been investigated to treat asthma, cystic fibrosis and interstitial lung disease (ILD). The direct ...

Circ Res, 2008

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