Induction of cytochrome P-450 RNA by porphyrogenic agents: on the nature of the coordinate induction with delta-aminolevulinate synthase in tissues of the chicken embryo.

1. We determined by cDNA-RNA solution hybridization analyses that in ovo administration of allylisopropylacetamide in combination with diethyl 1,4-dihydro-2,4,6-trimethyl-3,5-pyridinedicarboxylate increased the concentrations of cytochrome P-450 RNA in liver, kidney, and intestine of 18-day-old chicken embryos. 2. Similarly, the administration of testosterone to embryos caused elevations in the cytochrome P-450 RNA levels in liver and kidney. 3. The increases in cytochrome P-450 RNA concentrations occurred only in those tissues where elevations in delta-aminolevulinate (ALA) synthase activity and mRNA content were measured (liver, kidney and intestine) but not in tissues where the activity and RNA levels of ALA synthase did not change (heart, brain, lung). 4. The increases in the concentrations of the cytochrome P-450 RNA were not affected by loading embryos with ALA and FeCl3 at the time of administration of the inducers.