Rat cardiac muscarinic receptors. II. Influence of thyroid status and cardiac hypertrophy

P Robberecht, M Waelbroeck, M Claeys, AN Huu, P Chatelain and J Christophe

The effects of the thyroid state and of aortic stenosis on muscarinic cholinergic binding sites in heart membranes were compared (with proper controls) by simultaneously determining total and high-affinity binding sites and estimating low-affinity binding sites by difference. Hyper- and hypothyroidism induced decreased and increased concentration of high-affinity agonist binding sites, respectively, supporting the hypothesis that these sites were directly regulated by thyroid hormones. This was not the case for low-affinity binding sites, as they decreased in number in both hyper- and hypothyroidism. In hyperthyroid rats, this decreased number of low-affinity binding sites could be due to the rapidly developing cardiac hypertrophy. Indeed, cardiac hypertrophy provoked by aortic stenosis led also to a decreased concentration of low-affinity binding sites without affecting the concentration of high-affinity binding sites.

Volume 21, Issue 3, pp. 589-593, 05/01/1982
Copyright © 1982 by American Society for Pharmacology and Experimental Therapeutics

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