Elimination of isoproterenol-induced proline-rich protein biosynthesis in rat salivary glands after adult thyroidectomy.

Surgical thyroidectomy of adult rats resulted in a gradual decrease in beta-adrenergic receptor density on the cell surface of parotid and submandibular glands. The decrease in beta-adrenergic receptors was 29 and 50% by 2 and 4 weeks, respectively, for the parotid gland. In the submandibular gland, a decrease of 50% of the total beta-receptor density was evident after 2 weeks. After 4 weeks no further decrease in beta-adrenergic receptor was observed. Subsequent challenge of the salivary glands with chronic treatment of isoproterenol (beta-adrenergic receptor agonist) failed to induce proline-rich protein and glycoprotein biosynthesis in the submandibular gland 2 weeks after thyroidectomy, whereas the parotid gland showed induced proline-rich protein but not the glycoprotein synthesis. By 4 weeks the parotid gland did not show the induced synthesis of the glycoprotein or proline-rich proteins. The inability to induce protein synthesis was reflected by decreased cAMP accumulation in both glands after injection with isoproterenol. Partial reversal of these effects on protein synthesis and cAMP accumulation was obtained by triiodothyronine treatment of thyroidectomized rats.