Studies on Mitochondrial Protein Kinase Activity of Porcine Corpora Lutea*

Abstract

Activation of mitochondrial protein kinase and its role in regulation of [4-14MC]cholesterol conversion to [4- 14C]pregnenolone and [4-14C]progesterone were studied using mitochondria prepared from porcine corpora lutea. The presence of a cAMP-dependent protein kinase in luteal mitochondria was confirmed by using highly purified samples prepared by large scale zonal centrifugation. Slices of corpora lutea secreted almost 3 times more progesterone when incubated for 30 min with 10 μg LH/ml. The LH treatment of luteal tissue also resulted in an increase in endogenous protein kinase activity (measured without cAMP) of mitochondria from 45.0 to 60.7 pmol 32P/mg protein min. However, the LH treatment of corpora lutea did not significantly change [4-14C]cholesterol conversion activity. When isolated intact luteal mitochondria were incubated with cAMP, almost all of themitochondrial protein kinase was activated, but there was no change in the [4-14C]cholesterol conversion activity of these mitochondria. The addi...