Relative expression of aromatase cytochrome P450 in human fetal tissues as determined by competitive polymerase chain reaction amplification.

The aromatase enzyme complex is responsible for the conversion of C19 steroids to estrogens. Aromatase activities ranging from moderate to very low have been measured in human fetal tissues. The inability to demonstrate aromatase cytochrome P450 (P450AROM) messenger RNA (mRNA) in several fetal tissues by northern blotting has been attributed to low levels of specific message. In order to identify and compare P450AROM mRNA levels in fetal tissues, we developed a specific competitive polymerase chain reaction amplification technique. This reaction uses coamplification of a rat P450AROM complementary RNA to normalize differences in amplification efficiencies. Using this technique, P450AROM mRNA was identified in all fetal tissues studied including; liver, lung, brain, skin, intestine, kidney, spleen, and heart. Fetal liver contained far more P450AROM mRNA per total RNA than any other tissues studied. Fetal brain and intestine also tended to have slightly higher levels than other tissues.