VARIATIONS IN IMMUNOREACTIVITY FOR PHENOBARBITAL-INDUCIBLE AND 3-METHYLCHOLANTHRENE-INDUCIBLE CYTOCHROMES-P-450, AND NADPH-CYTOCHROME-P-450REDUCTASE IN RAT-LIVER OVER 24 HOURS

To reveal distribution patterns of phenobarbital- and 3-methylcholanth rene-inducible cytochromes P-450 (PB and MC) and NADPH-cytochrome P-45 0 reductase (P-450red) within the liver acinus of untreated rats, and their variations over 24 h, hepatic samples were examined by immunohis tochemistry and image-analyzer at evenly spaced six time points over 2 4 h. When examined in semi-thin sections obtained from Epon-embedded, freeze-dried, and paraformaldehyde vapor-phase fixed materials, the im munoreactivity for these enzymes showed different distribution pattern s within the liver acinus. Immunodeposits for PB were predominantly di stributed in perivenous hepatocytes, whereas those for MC and P-450red were slightly more intense in periportal hepatocytes at each time poi nt. The immunoreactivity for PB and MC in both perivenous and periport al hepatocytes increased during the dark period, peaking early in the light period. These variations coincide well with our previous morphom etric results (Uchiyama and Asari, 1984); the volume and surface densi ties of rough endoplasmic reticulum (rER) in hepatocytes increased dur ing the dark period. On the other hand, weak fluctuation was demonstra ted in the immunoreactivity for P-450red in hepatocytes of both zones. These results suggest that PB and MC are retained in rER rather than smooth endoplasmic reticulum (sER) of hepatocytes obtained from untrea ted rats. These enzymes in sER may be short in their half-life spans.