GENDER-SPECIFIC AND DEVELOPMENTAL DIFFERENCES IN PROTEIN-KINASE-C ISOZYME EXPRESSION IN RAT-LIVER

Protein kinase C (PKC) activity is important in regulating cellular gr owth and differentiation and is believed to play a role in the promoti onal stage of carcinogenesis, To determine the effects of age and gend er on PKC expression, isozyme-specific antibodies and immunoblot analy ses were employed to examine the expression of PKC alpha, PKC beta, PK C gamma, PKC delta and PKC epsilon in the cytosolic and membrane fract ions isolated from hepatic tissue of 1, 3, 5 and 12 week old male or f emale rats, PKC alpha levels were comparable at 1 week of age in the r espective male and female hepatic fractions, In contrast, at 3, 5 and 12 weeks of age, cytosolic PKC alpha levels were similar to 2-, 5- and 7-fold greater, respectively, in females than in males, At 5 weeks of age, cytosolic levels of PKC delta were similar to 2-fold higher in f emales than in males, Other PKC isozymes were either below the limit o f detection (PKC gamma), or failed to exhibit any gender-related diffe rences (PKC beta and PKC epsilon), At 12 weeks of age, PKC activity wa s 1.7- or 2.4-fold greater in hepatic cytosol and membrane fractions, respectively, from females than in male samples, These results show di stinct gender-specific and developmental differences in hepatic PKC is ozyme expression, which may play a role in susceptibility to cancer.