The binding of (3H)-propylbenzilycholine mustard by longitudinal muscle strips from guinea-pig small intestine.

1 The synthesis of tritium labelled propylbenzilylcholine mustard ([(3)H]-PrBCM; N-2'-chloroethyl-N-[2'', 3''-(3)H(2)] propyl-2-aminoethyl benzilate) is described.2 The uptake by muscle strips was measured and shown to be considerably increased by previous immersion of the muscle in distilled water.3 A considerable part of the uptake is inhibited selectively by atropine, but not by nicotinic antagonists. A number of muscarinic agonists also inhibit uptake and their apparent affinity constants have been determined.4 The uptake by atropine-sensitive sites is temperature-insensitive, whereas the other sites are temperature-sensitive. Recovery is highly temperature-sensitive and there is good agreement between recovery of sensitivity to agonists and loss of radioactivity from the muscle.