Drugs online research references
Eur J Pharmacol. 1983 Oct 28;94(3-4):281-95.
Subclasses of muscarinic receptors in isolated gastric mucosal cells: receptor characterization and parietal cell function.
Albinus M, Winne D.
Muscarinic receptors were characterized in isolated intact chief and parietal cell enriched cell populations from canine and guinea-pig gastric mucosa by binding of tritiated N-methylscopolamine ([3H]NMS). Antagonist and agonist binding was studied by displacement of [3H]NMS with non-radioactive atropine, pirenzepine, pilocarpine and carbachol. Model analysis points to the existence of two binding sites in each of the two cell populations. The number of binding sites per cell was 1.7-1.8 times higher in parietal than in chief cell populations. Subclasses of muscarinic receptors as characterized by pirenzepine binding were compatible with the suggested A- and C- (high and low affinity) binding sites. The observation that in canine cells GMPPNP induced a conformational change of the high affinity binding site for pirenzepine could suggest that their proportion might depend on environmental factors. Binding parameters were related to specific parietal cell function as measured by aminopyrine accumulation as index for acid secretion. The carbachol effects depended on the calcium concentration and were competitively inhibited by pirenzepine. The physiological relevance of muscarinic receptor heterogeneity in gastric mucosal cells is unknown although the data support the hypothesis that involvement of muscarinic binding sites in calcium transport mechanisms connected with parietal cell function and possible conformational changes of the binding sites might be regulatory parameters in gastric secretory processes.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6689155&dopt=Abstract
Neuroendocrinology. 1978;26(2):85-92.
Influence of cholinergic receptor blockade and stimulation on the anterior pituitary mitotic activity.
Pawlikowski M, Stepien H, Wolaniuk A, Kunert-Radek J.
The effects of pilocarpine and atropine on the mitotic incidence in the anterior pituitary in male and ovariectomized estradiol-pretreated female rats was investigated. It was shown that pilocarpine stimulated, while atropine inhibited, the anterior pituitary mitotic activity. It was also shown that carbachol enhanced the mitotic incidence in the organ-cultured anterior pituitary and its effect was blocked by scopolamine. The existence of the muscarinic cholinergic receptor within the anterior pituitary, as well as its involvement in the control of the anterior pituitary mitotic activity, is suggested.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=673147&dopt=Abstract
J Neurochem. 1983 Aug;41(2):556-61.
Muscarinic acetylcholine receptors in Torpedo electric organ: effect of guanine nucleotides.
Dowdall MJ, Strange PG, Golds PR.
The effect of guanine nucleotides on the binding properties of presynaptic muscarinic receptors has been studied in a membrane preparation from the electric organ of Torpedo marmorata by measuring the competitive displacement of the radiolabelled antagonist, [3H]quinuclidinyl benzilate, by nonradioactive muscarinic ligands. The binding of the antagonists, atropine, scopolamine and pirenzepine was to a single class of sites [slope factors (pseudo Hill coefficients) close to 1] and was unaffected by 0.1 mM GTP. The binding of the N-methylated antagonists, N-methylatropine and N-methyl-scopolamine was more complex (slope factors less than 1) but also insensitive (N-methylatropine) to 0.1 mM GTP. Agonist binding was complex and could be resolved into two binding sites with relatively high and low affinities. The proportion of high-affinity sites varied with the nature of the agonist (15-80%). Agonist binding was depressed by 0.1 mM GTP, and the order of sensitivity was oxotremorine-M greater than carbamoylcholine greater than muscarine greater than acetylcholine greater than arecoline greater than oxotremorine. The binding of pilocarpine, a partial agonist, was unaffected by GTP. With carbamoylcholine as a test ligand the GTP effect on agonist binding was half-maximal at 12 microM. GDP and guanylylimidodiphosphate produced comparable inhibition of carbamoylcholine binding, but GMP and cyclic GMP were ineffective, as were various adenine nucleotides. Analysis of agonist binding in terms of a two-site model indicates that the predominant effect of guanine nucleotides is to reduce the number of sites of higher affinity.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6875553&dopt=Abstract
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