Protein kinase C in the developing rat liver, heart and brain

Ontogenic changes of protein kinase C in the rat liver, heart and cerebrum were examined from 17-day gestation until adult. Cerebral protein kinase C activity was 19 times less at 17-day fetal as compared to 15-day postnatum or older rats. The enzyme activity in the heart was generally higher in the neonatal period than the adult, but was not correlated with the previously reported α₁-adrenergic and cholinergic receptor ontogeny. Likewise in the liver, the enzyme activity was not correlated with previously reported α₁-adrenergic and vasopressin receptor ontogeny. No correlation between protein kinase C and cyclic AMP-dependent protein kinase activities was found among these tissues. The enzyme distribution expressed by a cytosol/particulate ratio of 0.72, 2.41 and 0.64 in the liver, heart and brain, respectively, in 20-day fetus was similar to adult values. We conclude that there is a discrete ontogenic pattern of protein kinase (in each organ and its does not seem to be correlated with the ontogenic pattern of hormone receptors which relate to phosphatidylinositol breakdown. The precise role of protein kinase C in relationship to growth and differentiation needs to be further investigated.