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 m uscle and ventricular cardiac muscle was examined in ovariectomized ra ts pretreated with estradiol-17 beta alone or with estradiol-17 beta a nd progesterone. Protein kinase C isozyme expression was examined in m embrane and cytosolic subcellular fractions by immunoblot analysis usi ng antisera specific for alpha, gamma, beta 1, beta 2, delta, epsilon, zeta, and theta isozymes. All isozymes were detectable in positive co ntrol brain extracts. The predominant isozymes in the myometrium were delta and beta 2 while in the ventricle, beta 2 and zeta were the domi nant forms. In unstimulated tissues, all isozymes except PKC-delta, we re 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 signif icantly affected protein kinase C expression in cardiac muscle. These data suggest that estradiol, which increases uterine muscle hypertroph y and contractility, may exert these effects by increasing membrane-as sociated protein kinase C expression in a tissue-specific manner.