Age-dependent changes in response of rat prostatic tissues to isoproterenol and forskolin: changes with sexual maturation in function of G proteins.

Developmental changes in the responses of rat ventral prostate to isoproterenol (IPR) and forskolin (F) were studied in relation to the function of beta-adrenoceptor-adenylate cyclase system. The response of adenylate cyclase in the tissues to IPR at 10(-7)M and above was steadily enhanced after birth and reached a maximum at 12 weeks, followed by a decrease with age. In contrast, the response of the enzyme to F at 10(-7)M and above was highest at 2 weeks, but thereafter decreased. The changes in the response of the enzyme to IPR coincided with changes in the beta-adrenoceptor density and the binding ability of GTP binding proteins (G proteins) to GTP. The ADP-ribosylation of inhibitory G proteins (Gi proteins) catalyzed by pertussis toxin (IAP) decreased 70% in the tissues from 4 to 8 weeks, and then maintained this level. On the other hand, the ADP-ribosylation of stimulatory G proteins (Gs proteins) catalyzed by cholera toxin (CT) increased only 20% in the tissues from 2 to 4 weeks. Thus, the ratio of ADP-ribosylation of Gs to that of Gi significantly increased from 4 weeks, reaching a maximum at 12 weeks, but thereafter decreased gradually with age. These changes paralleled those in the function of G proteins and the response of the enzyme to IPR. It is suggested that the rapid and marked decrease in apparent level of Gi proteins in the rat ventral prostate after 4 weeks may have a key role in controlling the function of the beta-adrenoceptor-adenylate cyclase system in the tissues.