The effect of portacaval transposition on hepatic cytochrome P-450 in the rat

The effects of portacaval anastomosis and portacaval transposition on colloidal radiogold fractional clearance and on hepatic cytochrome P-450 level were compared in the rat. Colloidal radiogold fractional clearance was significantly lower in rats with portacaval anastomosis (0.556 +/- 0.188 min-1 (mean +/- 1 SD)) than in sham-operated animals (0.842 +/- 0.151 min-1); hepatic cytochrome P-450 level was likewise lower in the former (0.60 +/- 0.14) nmol/mg of microsomal proteins) than in the latter (0.83 +/- 0.12 nmol/mg of microsomal proteins). Colloidal radiogold fractional clearance was not different in rats with portacaval transposition (0.808 +/- 0.201 min-1) and in sham-operated animals (0.798 +/- 0.064 min-1); hepatic cytochrome P-450 level was significantly lower in the former (0.55 +/- 0.07 nmol/mg of microsomal proteins) than in the latter (0.76 +/- 0.17 nmol/mg of microsomal proteins). If colloidal radiogold clearance is assumed to be an index of liver blood flow, these results suggest that portacaval anastomosis induces a decrease, and portocaval transposition produces no change, in liver blood flow. It is concluded that the decrease in hepatic cytochrome P-450 level in the rat with portacaval anastomosis is not merely the consequence of reduced blood flow, but rather results from deprivation of a substance or substances present in portal blood and contributing to maintenance of the cytochrome level.