Changes in relative levels of guanosine-3':5'-monophosphate-dependent and adenosine-3':5'-monophosphate-dependent protein kinases in lung, heart, and brain of developing guinea pigs.

Canges in relative levels of protein kinases (ATP:protein phosphotransferase, EC 2.7.1.37) stimulated by either guanosine 3':5'-monophosphate (cyclic-GMP) or adenosine 3':5'-monophosphate (cyclic-AMP) were examined in extracts of the lung, heart, brain, and liver from guinea pigs at various stages of development. The level of cyclic-GMP-dependent protein kinase in the fetal lung, which was found to be the highest of any mammalian tissue samples examined, declined during development. On the other hand, the level of cyclic-AMP-dependent protein kinase in the same extracts, which was initially lower than that of the cyclic-GMP-dependent enzyme, increased during development and reached a level higher than that of the cyclic-GMP-dependent enzyme when the animals reached maturity. This reciprocal change in level of the two classes of protein kinases in developing lung was demonstrated further by chromatographing the extracts on Sephadex G-200 and quantitating the activity of the isolated enzymes. A decrease in the ratio of the two classes of protein kinases qualitatively similar to that seen in the lung was also noted in the developing heart. An increase in the ratio of the enzymes, however, was seen in the developing brain. Unlike in the lung, heart, and brain, no change in relative level and ratio of the enzymes was noted in liver during development. These results suggest that a balance between the effects of cyclic-GMP-dependent and cyclic-AMP-dependent protein kinases may be important in normal development of certain tissues.