Age-dependent changes in the phosphorylation of nuclear proteins of submandibular glands in isoproterenol-treated rats

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.

Dephosphorylation of nuclear non-histone proteins in submandibular glands of rats treated with isoproterenol

Protein phosphatase that removed [32P]phosphate from non-histone proteins, i.e., phenol-soluble acidic proteins, more rapidly and strongly than from histone proteins was present in nuclei of rat submandibular glands, but was not associated with chromatin. Cyclic AMP (10(-4)-10(-2) mM) stimulated the dephosphorylation of non-histone proteins, but not that of histone proteins. After a single injection of isoproterenol (IPR), the dephosphorylation of non-histone proteins in rat submandibular gland nuclei increased within 15 min, reached a maximum in 30 min and returned to normal control levels within 4 h. The stimulation of dephosphorylation of non-histone proteins induced by IPR was not observed after prior treatment of the animals with dichloroisoproterenol. The dephosphorylation of histone proteins was not affected by the injection of IPR. Stimulation of beta-adrenoceptors with IPR in rat submandibular glands resulted in increase in cyclic AMP and decrease in RNA synthesis in the tissues in the first few hours after the injection. This decrease in RNA synthesis was temporary and was preceded by the increase in cyclic AMP level and in the dephosphorylation of non-histone acidic proteins in the tissues. These results suggest that protein phosphatase in nuclei plays an important part in the events controlling RNA synthesis by regulating the state of phosphorylation of non-histone acidic proteins. In addition, the phosphatase may be regulated by a function of the cytoplasmic membranes.