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G T Bolger

Publications and source records attributed to G T Bolger.

58 records · Page 4Linked to original sources
PubMed1982

Binding of [3H]nimodipine to cardiac and smooth muscle membranes.

Specific binding of [3H]nimodipine to membranes from rat ventricle and guinea pig ileal longitudinal smooth muscle was studied. Dissociation constants were 0.24 and 0.12 nM, and the maximal number of binding sites were 0.4 and 0.75 pmol/mg protein for cardiac and smooth muscle, respectively. The values obtained for both types of muscle were similar to those obtained for [3H]nitrendipine binding, as were the potencies of a series of dihydropyridines for competing with [3H]nimodipine. These results support the hypothesis that the binding site characterized is that mediating the pharmacological effects of these compounds.

Animals↗
PubMed1982

Muscarinic receptors in guinea pig ileum. A study by agonist--3H-labelled antagonist competition.

A series of muscarinic agonists (n = 18) derived from dioxolane, furan, piperidine, and thiacyclohexane ring structures which have a degree of conformational restraint have been examined in guinea pig ileal smooth muscle. Binding to muscarinic receptors was determined by competition with 3H-labelled (-)-quinuclidinyl benzilate. Agonist binding was characterized by shallow displacement curves and Hill coefficients (nH) of less than 1. Binding (K1) was resolved into high (K1) and low (K2) affinity components. Correlations between drug-receptor binding and pharmacological activity were examined. A good correlation was found between K1 and K2 (pK1 = 1.33 X pK2 - 0.1), suggesting that the structural requirements for binding at low and high affinity sites are similar. Good correlations also exist between pK1 and pD2 (pK1 = 0.63 X pD2 + 1.27, furans and dioxolanes; pK1 = 0.71 X pD2 + 1.30, piperidines and thiacyclohexanes) confirming that a pharmacologically potent agonist has a high binding affinity. Although K1 represents only an "average" binding affinity its correlation with pD2 is better than those between pK1 or pK2 and pD2. The significance of these several correlations is discussed and some general limitations to the correlation of binding and response data at pharmacological receptors are noted.

Animals↗
PubMed1982

Calcium-channel antagonist binding to isolated vascular smooth muscle membranes.

The binding characteristics of the calcium-channel antagonist nitrendipine, an analog of nifedipine, have been measured in plasma membrane enriched microsomal fractions from the canine thoracic aorta, canine mesenteric artery, and rat mesenteric artery. The dissociation constants, KD, for the high-affinity binding sites were, respectively, 0.308, 0.254, and 0.101 nM and Bmax values for binding capacity were 20.3, 25.0, and 18.0 fmol/mg of microsomal protein. Studies with isolated tissues, in which the sensitivity of the high potassium mechanical response to nitrendipine was determined, indicate that the apparent KD for nitrendipine in the canine mesenteric artery, as reflected by the IC50 (mean inhibition constant) value, is 4.5-5.3 nM and for the rat mesenteric artery 2.5-6.6 nM.

Animals↗