Developmental alterations of adenylate cyclase in rat parotid glands

We have studied the postnatal alterations of the neurotransmitter receptors in rat parotid gland, and found that the number of ƒÀ-adrenoceptors in the tissues and their affinity for the ƒÀ-agonists increased significantly during development and that these changes were coupled with amylase secretion by ƒÀ-agonist from the tissues. In this experiment, developmental changes in the adenylate cyclase in rat parotid gland cells were studies by using forskolin or isoproterenol. Forskolin produced the rapid increases in cyclic AMP contents in the parotid tissues of 8 weeks old rats and caused amylase secretion from the tissues. The increases in cyclic AMP contents by forskolin were potentiated by 3-isobutyl-1-methylxanthine (IBMX). Calcium had an important role in the secretion of amylase by forskolin. Tolbutamide blocked the amylase secretion by forskolin at the concentration which inhibited cyclic AMP dependent protein kinase activity. The content of cyclic AMP accumulated by forskolin (10 ƒÊM) in parotid tissues of 1 week old rats was 10 fold higher than that in the tissues of 8 weeks old rats. These changes in the contents of cyclic AMP accumulated by forskolin during development were coupled with amylase secretion from the tissues. The changes in the response of the tissues to forskolin were clearly observed in the tissues of rats between 2 and 4 weeks after birth. On the other hand, cyclic AMP contents accumulated by isoproterenol (1 ƒÊM) in parotid tissues of 1 week old rats were very low, but those increased markedly in the rat tissues of 4 and 8 weeks after birth. Isoproterenol potentiated the accumulation of cyclic AMP by forskolin in the tissues from 1 to 8 weeks old rats. These results indicate that the response of adenylate cyclase of rat parotid tissues to forskolin decreases markedly during development, but that of ƒÀ-adrenoceptors of the tissues to isoproterenol increased significantly during the same period.