The effect of ionic strength on cardiac muscarinic receptors.
The binding of N-methylscopolamine (NMS) and carbachol to muscarinic receptors in the rat heart has been measured as a function of ionic strength (mu). The binding of NMS was reduced by 3.69 fold for a 10 fold increase in ionic strength. The binding of carbachol was affected in two ways. Firstly, the proportions of the subsites were changed. Above mu = 0.5 M, the superhigh (SH) subsite was converted into the low (L) subsite and above mu = 0.8 M, the high (H) subsite was also converted into the L subsite. Therefore, at high ionic strength, no agonist-determined subsites can be detected. In addition, increase in ionic strength reduced the binding of carbachol to all subsites and to a much greater extent than for NMS.
D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D002217:Carbachol / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008566:Membranes / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D019832:N-Methylscopolamine; D051381:Rats; D011919:Rats, Inbred Strains; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism*; D012602:Scopolamine Derivatives / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology
D011976:Receptors, Muscarinic; D012602:Scopolamine Derivatives; D012965:Sodium Chloride; D002217:Carbachol; D019832:N-Methylscopolamine