Ovarian Cyclic Adenosine Monophosphate-Dependent Protein Kinase Activity: Ontogeny and Effect of Gonadotropins

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Abstract
The ontogeny of ovarian cyclic AMP-binding and protein kinase activities during the postnatal development of the rat, and the effect of LH [luteinizing hormone] and FSH [follicle stimulating hormone] administration on ovarian cyclic AMP-binding and protein kinase activities in 5 day old and in hypophysectomized rats was examined. Ovaries of 4 to 8 day old rats possessed little or no measurable cyclic AMP-binding and protein kinase activities. Subsequent postnatal development occurred in 3 distinct phases. During the 1st phase, ovarian cyclic AMP-binding and protein kinase activities increased progressively from age 8 days to age 23 days, when adult levels were observed. Protein kinase activity declined markedly during the 2nd postnatal developmental phase from days 24 to 26, lost its cyclic AMP-dependency, and became refractory to stimulation by cyclic AMP. Studies employing a heat-stable protein kinase inhibitor protein isolated from rabbit skeletal muscle suggest that ovarian protein kinase activity during the refractory period was largely of the cyclic AMP-independent variety. During the 3rd postnatal phase, comprising days 30 to 40, ovarian cyclic AMP-binding and protein kinase activities increased to levels seen in sexually mature rats. Protein kinase cyclic AMP-dependency which was lost during the refractory 2nd postnatal period was fully restored during the 3rd phase. Administration of FSH or LH led to a marked increase of ovarian cyclic AMP-binding and protein kinase activities in 5 day old rats. Hypophysectomy of 20 day old rats caused a significant reduction of the cyclic AMP-binding and protein kinase activities in a 27,000 .times. g supernatant fraction, and in the mitochondrial, microsomal and 105,000 .times. g supernatant fraction. The decreased cyclic AMP-binding and protein kinase activities of these fractions could be partially restored by FSH or LH treatment of the hypophysectomized rats. Ovarian cyclic AMP-binding and protein kinase activities, and the ability of ovarian protein kinase to respond to cyclic AMP are gradually acquired after the 1st postnatal week. The postnatal development of ovarian protein kinase and cyclic AMP-binding activities presumably involves the participation of FSH and LH, although the precise mechanism of LH and FSH action remains to be established.