Endocrinology, Vol 103, 420-430, Copyright © 1978 by Endocrine Society

ARTICLES

Rabbit ovarian protein kinases. I. Effect of an ovulatory dose of human chorionic gonadotropin or luteinizing hormone on the subcellular distribution of follicular and luteal protein kinases

M Hunzicker-Dunn and RA Jungmann

Studies on the subcellular distribution of protein kinase activity in popped estrous follicles from rabbit ovaries revealed that 15% of the total cellular protein kinase activity was compartmentalized in the nuclear, mitochondrial, and microsomal fractions. About 50% of the particulate protein kinase activity was unaffected by the heat-stable protein kinase inhibitor and was thus cAMP-independent. The majority of cellular protein kinase activity was identified in the 105,000 X g supernatant fraction as cAMP-dependent. hCG- or coital-induced ovulation and subsequent corpus luteum (CL) formation, and hCG-induced luteal regression promoted changes and a redistribution of protein kinase activity among the subcellular fractions. In follicles, hCG promoted a transient decline of nuclear protein kinase activity as well as transient increases of the relative amount of protein kinases localized in the microsomal fractions before ovulation. In CL induced by a fertile mating, the specific activity as well as the total amount of protein kinases in the nuclear fraction were reduced 2-fold. Mitochondrial protein kinase activity from CL of pseudopregnancy and pregnancy was reduced 2-fold. The relative amount of protein kinase activity in microsomes of CL was increased 2-fold, but the specific activity was not affected. hCG-induced luteal regression resulted in a transient decline of the nuclear protein kinase activity in CL of 4-day pseudopregnant rabbits. In interstitial tissue, the specific activity of the nuclear protein kinase was increased over luteal levels, the mitochondrial-specific protein kinase remained at the reduced luteal levels, and the microsomal and cytosol protein kinase specific activities increased 2-fold. Studies with the heat-stable protein kinase inhibitor revealed that the hCG- or coital-induced redistribution of intracellular protein kinase affected both the cAMP- dependent and cAMP-independent activity to a similar degree and no changes of the relative distribution of cAMP-dependent vs. cAMP- independent activity were observed. These results indicate that the intracellular distribution and enzymatic activity of cAMP-dependent protein kinases in ovarian structures are subject to regulation by LH (hCG) and depend upon the various reproductive stages of the rabbit.