Muscarinic acetylcholine receptors of rat lymphocytes.

The muscarinic acetylcholine receptors on rat lymphocytes were determined by [3H]quinuclidinyl benzilate binding studies. Binding of [3H]quinuclidinyl benzilate is rapid (half saturation occurred within 120 s) and highly specific. Muscarinic receptors reveal high lability. The number of receptors on plasma membrane depends on time of incubation as well as on composition of incubation medium. Lymphocytes incubated in nutrient-deficient media lose their surface receptors; enrichment of the medium causes reappearance of the receptors. Appearance of [3H]quinuclidinyl benzilate-binding sites in the incubation medium was under conditions in which binding to lymphocytes was decreased. It is concluded that the number of plasma membrane receptors on rat lymphocytes represents the dynamic steady state in which newly synthesized and degraded receptors are balanced.