Induction of cytochromes P450IA1 and P450IA2 as determined by solution hybridization.

Two oligodeoxyribonucleotides were synthesized that were specific for the messenger RNAs for the polycyclic hydrocarbon-inducible cytochromes P450IA1 and P450IA2. The solution hybridization technique was modified for the use of these oligodeoxyribonucleotide probes so as to increase the sensitivity and specificity of this method. Using this technique, the steady-state levels of the mRNAs for cytochromes P450IA1 and P450IA2 in control rat liver were determined to be less than 3 and 6 molecules/cell, and 1.8 and 4.0 attomol/micrograms poly (A)+ RNA, respectively. At 15 hr after induction with 3-methylcholanthrene, the steady-state levels of the mRNAs for P450IA1 and P450IA2 were 68 and 200 molecules/cell, and 41.6 and 123 attomol/micrograms poly (A)+ RNA.