Tissue-specific expression and induction by phenobarbital of rabbit NADPH-cytochrome P450 reductase

We investigated the expression of NADPH-cytochrome P450 reductase (P450 reductase) in various tissues from rabbits. The size of RNA from liver, lung, and kidney of rabbit was compared. Northern hybridization with total RNA indicated that the P450 reductase mRNA in liver was 21 S size, which corresponds to 2.3 kb, and there was no difference in the size of P450 reductase mRNA between liver and extrahepatic tissues. The tissue-specific expression of P450 reductase was investigated by measuring its activity and mRNA content in these tissues of rabbit. To compare the levels of the reductase mRNA between rabbit tissues, the amount of b-actin mRNA for normalization was used. A good correlation was observed between the mRNA and the enzyme activities of P450 reductase in rabbit liver, lung, and kidney. The increase in the activity by phenobarbital (PB) treatment was not observed in any of the tissues. The amount of P450 reductase mRNA in the liver was slightly increased and that in the kidney was not changed, while the level of P450 reductase mRNA in the lung was induced approximately 2-fold. These results suggest that P450 reductase mRNA in rabbit tissues, which is transcribed from an identical gene, is translated to an identical protein molecule, and that the response of P450 reductase mRNA and protein to induction by PB in each tissue is different among the different tissues of the rabbit.