We report on hormonal regulation of protein kinases in the rabbit myometrium. The injection of estrogen or progesterone produced 5.2�0.7- or 4.7�0.4-fold increases, respectively, of the total activity when histone was used as the substrate in the cytosol fraction of the tissue. The analysis of the activity by DEAE-cellulose column chromatography revealed that estrogen had no effect on increases in the levels in both types I and II cAMP-dependent protein kinases, on the basis of mg protein, while progesterone produced a 50% decrease in type I cAM P-dependent protein kinase and a 50% increase in type l! cAMP dependent protein kinase. Thus, the activity ratio of types I! to type I did not change by treatment with estrogen and increased from 2.8 to 7.9 with progesterone administration. As the activity patterns by treatment with human chorionic gonadotropin closely resembled those seen with progesterone, our findings in case of the latter hormone are probably valid. The results indicate that the levels of protein kinases in the myometrium are altered in response to estrogen and progesterone and may possibly be involved in the physiological functions of the tissue.
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