Androgen-linked control of carbonic anhydrase III expression occurs in rat perivenous hepatocytes; an...

Carbonic anhydrase (CA) isozymes CAII and CAIII were assayed by a radioimmunosorbent technique in liver cytosolic fractions and in isolated hepatocytes of adult male and female rats. Male livers contained 0.16 mg of CAII and 57 mg of CAIII per g cytosolic protein. Corresponding values for female livers were 0.34 mg CAII and 4 mg CAIII. Similar values and differences between CAII and III were found in isolated hepatocytes. Neonatal and adult castration of males reduced the CAIII levels to those of the females. Treatment with testosterone for three weeks restored the copulatory behaviour in the males castrated at adult age, but restored only partially the levels of CAIII. No significant effects of the endocrine manipulations were seen on CAII. Oophorectomy, with or without testosterone substitution, had no significant effect on CAII and CAIII levels in female rats. Immunohistochemistry and histochemistry showed that the regulation of CAIII is confined to perivenous hepatocytes. CAIII can therefore serve as a useful marker in the separation of these cells. CAIII appears to belong to the proteins and enzymes of the rat liver, known to be regulated via the hypothalamo-pituitary-liver axis. It may be used as a model of gene regulation in perivenous hepatocytes.