Estrogen increases the expression of uterine protein kinase C isozymes in a tissue specific manner

The pattern of protein kinase C isozyme expression in uterine smooth muscle and ventricular cardiac muscle was examined in ovariectomized rats pretreated with estradiol-17 beta alone or with estradiol-17 beta and progesterone. Protein kinase C isozyme expression was examined in membrane and cytosolic subcellular fractions by immunoblot analysis using antisera specific for alpha, gamma, beta 1, beta 2, delta, epsilon, zeta, theta isozymes. All isozymes were detectable in positive control brain extracts. The predominant isozymes in the myometrium were delta and beta 2 while in the ventricle, beta 2 and zeta were the dominant forms. In unstimulated tissues, all isozymes except PKC-delta, were predominantly found in the cytosolic compartment. Both estrogen and progesterone increased membrane-associated isozyme expression 35-125% in uterine muscle. Neither estrogen nor progesterone treatment significantly affected protein kinase C expression in cardiac muscle. These data suggest that estradiol, which increases uterine muscle hypertrophy and contractility, may exert these effects by increasing membrane-associated protein kinase C expression in a tissue-specific manner.