The reversible inability of isoproterenol-activated parotid gland cells to initiate DNA synthesis in the hypocalcemic thyroparathyroidectomized rat.

An intraperitoneal injection of the beta-adrenergic drug dl-isoproterenol hydrochloride (100 mg/kg body weight) into male (190-210 g) albino rats caused two cyclic AMP surges (peaking at 10 minutes and again between 8 and 12 hours) and the initiation of DNA synthesis (between 16 and 20 hours) in the parotid glands. The parotid cells in hypocalcemic thyroparathyroidectomized rats still responded to isoproterenol injection by generating the two cyclic AMP surges, but they did not initiate DNA synthesis unless a blood calcium-elevating combination of parathyroid hormone (50 USP units/100 g of body weight) and 1 alpha,25(OH)2 vitamin D3 (200 pmoles/100 g of body weight) was injected along with the isoproterenol.