Egon Novak

Developmental changes in cyclic AMP, protein kinase, phosphorylase kinase, and phosphorylase in liver, heart, and skeletal muscle of the rat.

Abstract Changes in cyclic AMP, protein kinase, phosphorylase kinase, and phosphorylase levels were examined during development in the rat. In liver, cyclic AMP increased prenatally and for the first 10 postnatal days; protein kinase levels (both cyclic AMP-dependent and independent activities) were high prenatally and declined during the first 10 postnatal days. Both phosphorylase and phosphorylase kinase in liver increased rapidly prenatally and more slowly postnatally. In heart and skeletal muscle cyclic AMP increased prenatally and for the first 10 days after birth, then declined. Protein kinase in both these tissues was highest prenatally and declined perinatally. In heart and skeletal muscle phosphorylase and phosphorylase kinase activities were extremely low prenatally although both enzymes were largely in their activated forms. Postnatally the nonactive form of both enzymes increased greatly throughout 30 postnatal days. In all three tissues, particularly heart and skeletal muscle, these changes could not be correlated with levels of tissue glycogen.

Changes in interscapular brown adipose tissue of the rat during perinatal and early postnatal development and after cold acclimation. V. Adenyl cyclase, cyclic amp, protein kinase, phosphorylase, phosphorylase kinase, and glycogen

Abstract 1. 1. The glycogen content of rat brown adipose tissue decreased dramatically at birth. 2. 2. Cyclic AMP levels reached a peak just prior to birth and decreased postnatally. Adenyl cyclase activity increased steadily up to the 20th postnatal day. 3. 3. Cyclic AMP-dependent protein kinase activity increased perinatally and decreased after the 20th postnatal day. 4. 4. Phosphorylase and phosphorylase kinase were both present primarily in the activated form prenatally and both increased significantly immediately before birth; then declined rapidly. Non-active phosphorylase followed a similar developmental pattern but the non-activated form of phosphorylase kinase continued to increase for 20 postnatal days. 5. 5. The DNA and RNA content of the tissue was highest during prenatal life. 6. 6. Cold exposure of 20-day-old rats caused increases in total phosphorylase, protein kinase, adenyl cyclase and cyclic AMP levels when expressed on a tissue fresh-weight basis.