Rabbit Ovarian Protein Kinases. II. Effect of an Ovulatory Dose of Human Chorionic Gonadotropin or Luteinizing Hormone on the Multiplicity of Follicular and Luteal Protein Kinases*

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Abstract
DEAE-cellulose chromatography of the 105,000 .times. g supernatant fraction (cytosol) obtained from popped estrous rabbit follicles revealed the presence of a single form of c[cyclic]AMP-dependent protein kinase, designated protein kinase 3. The i.v. injection of an ovulatory dose of hCG [human chorionic gonadotropin] to estrous rabbits promoted the appearance of a 2nd, transient peak of cytosol cAMP-dependent protein kinase, protein kinase 1. Protein kinase 1 was detected within 10 min of hCG administration but had regressed to undetectable levels by 24 h in corpora lutea (CL) of pseudopregnancy and by 72 h in CL of pregnancy. Ovulation and subsequent CL formation were accompanied by the appearance of a 3rd form of cAMP-dependent protein kinase, designated protein kinase 2. Protein kinase 2 was present within 2 h after hCG administration and persisted as a major form of cytosol cAMP-dependent protein kinase throughout the life span of CL. All 3 forms of protein kinase were inhibited by the heat-stable protein kinase inhibitor from rabbit skeletal muscle, possessed cAMP-binding activity, and were markedly stimulated by 10-7 M cAMP. Activity of protein kinase 3 in CL of pregnancy, in corpora albicantia and in interstitial tissue was markedly greater than that in follicles or in CL of pseudopregnancy, while the activity of protein kinase 2 remained relatively constant throughout the luteal life span. The i.v. injection of a luteolytic dose of hCG to 4 day pseudopregnant rabbits promoted no alterations of the protein kinase elution profile upon DEAE-cellulose chromatography of the luteal cytosol obtained 10 min to 3 days post-hCG injection. However, with dedifferentiation of corpora albicantia into interstitial tissue, the cAMP dependency of protein kinase 2 was reduced. The enzymatic activity and multiplicity of cAMP-dependent protein kinases in the cytosol of ovarian structures apparently are subject to regulation by LH [luteinizing hormone] (hCG) and depend upon various reproductive stages of the rabbit.