title: Effect of urea-treatment on agonist binding affinity of the muscarinic acetylcholine receptor.
abstract: Urea-treatment of the microsome fraction of the heart of guinea-pigs caused selective reduction in the apparent affinity of an agonist (carbachol), but not an antagonist (atropine), to muscarinic acetylcholine receptors (mAChR), measured as inhibition of binding of 3H-quinuclidinyl benzilate (3H-QNB). This effect was similar to that of Gpp (NH)p. The effects of urea-treatment and Gpp (NH)p were not additive. On the other hand, treatment of the microsome fraction with 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB) increased the apparent affinity of agonist, but not antagonist. The effect of DTNB predominated over those of urea-treatment and Gpp (NH)p, when these treatments were combined with DTNB.
mesh_terms: D000818:Animals; D001285:Atropine / Q000378:metabolism; D001667:Binding, Competitive; D002217:Carbachol / Q000378:metabolism*; D004228:Dithionitrobenzoic Acid / Q000494:pharmacology; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D006168:Guinea Pigs; D008297:Male; D008861:Microsomes / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D011813:Quinuclidinyl Benzilate / Q000378:metabolism; D011950:Receptors, Cholinergic / Q000378:metabolism*; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism*; D014508:Urea / Q000494:pharmacology*
chemical_list: D011950:Receptors, Cholinergic; D011976:Receptors, Muscarinic; D006165:Guanylyl Imidodiphosphate; D011813:Quinuclidinyl Benzilate; D001285:Atropine; D014508:Urea; D002217:Carbachol; D004228:Dithionitrobenzoic Acid