Gender-specific and developmental differences in protein kinase C isozyme expression in rat liver.

Abstract

Protein kinase C (PKC) activity is important in regulating cellular growth and differentiation and is believed to play a role in the promotional stage of carcinogenesis. To determine the effects of age and gender on PKC expression, isozyme-specific antibodies and immunoblot analyses were employed to examine the expression of PKC alpha, PKC beta, PKC gamma, PKC delta and PKC epsilon in the cytosolic and membrane fractions isolated from hepatic tissue of 1, 3, 5 and 12 week old male or female rats. PKC alpha levels were comparable at 1 week of age in the respective male and female hepatic fractions. In contrast, at 3, 5 and 12 weeks of age, cytosolic PKC alpha levels were approximately 2-, 5- and 7-fold greater, respectively, in females than in males. At 5 weeks of age, cytosolic levels of PKC delta were approximately 2-fold higher in females than in males. Other PKC isozymes were either below the limit of detection (PKC gamma), or failed to exhibit any gender-related differences (PKC beta and PKC epsilon). At 12 weeks of age, PKC activity was 1.7- or 2.4-fold greater in hepatic cytosol and membrane fractions, respectively, from females than in male samples. These results show distinct gender-specific and developmental differences in hepatic PKC isozyme expression, which may play a role in susceptibility to cancer.