| Abstract: | Isoproterenol induces both the secretion of protein and the stimulation of DNA synthesis and growth in rat salivary glands. The specific binding of the labelled beta-adrenergic antagonist 3H]dihydroalprenolol has been used to measure the number of beta-adrenergic receptors in rat parotid glands during isoproterenol-induced growth. Isoproterenol-enlarged glands display no change in the specific binding capacity per gland for 3H]-dihydroalprenolol compared with normal tissue. Catecholamine sensitive adenylate cyclase activity varies independently of the number of specific 3H]dihydroalprenolol binding sites during isoproterenol-induced growth. Previously-described di-ferences in optimal isoproterenol doses which produce protein secretion and stimulation of DNA synthesis may reflect different responses to various rates of receptor occupancy, or may be due to the presence of more than one type of beta-adrenergic receptor. |
