Radioprotection of the rat parotid gland by WR-2721 and isoproterenol and its modification by propranolol.

The aminothiol WR-2721 and beta-adrenergic agonist isoproterenol both conferred considerable radioprotection to the rat parotid gland. Isoproterenol acts on the beta-receptor, and its specific antagonist, propranolol, eliminated isoproterenol's protective effect, implicating the beta-receptor and possibly cAMP in the mechanism of the protection. Since other sulfhydryl-containing protectants have been shown to elevate cAMP it was reasoned that WR-2721 might do so as well. However, the radioprotection conferred by WR-2721 was not reduced by propranolol, showing that the beta-receptor played no part in WR-2721's action. The possible role of cAMP in radioprotection by isoproterenol is discussed.