Alpha- and beta-adrenergic receptors of the rat salivary gland. Elevation after chemical sympathectomy.

Binding of [3H]dihydroergokryptine and [3H]dihydroalprenolol to membrane preparations from rat submaxillary gland was measured to characterize the alpha- and beta-adrenergic receptors, respectively. Kinetic analysis of the data revealed a high affinity binding site for each radioligand. Inhibition of binding at each site was stereospecific for the active isomer of the catecholamine used. The greater ability of a beta1 than beta2 specific beta-adrenergic antagonist to displace [3H]dihydroalprenolol binding indicated that this binding site was of the beta1 type. Chemical sympathectomy with reserpine or 6-hydroxydopamine resulted in a significant increase in both [3H]dihydroalprenolol and [3H]dihydroergokryptine binding in the rat submaxillary gland. 3scatchard analysis of the data indicated that these increases in binding were due to a change in total number of binding sites for [3H]dihydroergokryptine and [3H]dihydroalprenolol with little change in apparent affinities. This suggests that changes in alpha- and beta-adrenergic receptor density may be important in the development of supersensitivity in salivary glands after reserpine and 6-hydroxydopamine treatment.