Monoclonal antibody directed detection of cytochrome P-450 (PCN) in human fetal liver

Monoclonal antibodies (MAbs) raised to rat liver cytochrome P-450s induced by phenobarbital, 3-methylcholanthrene, and pregnenolone-16 alpha-carbonitrile were used to detect these epitope specific P-450s in human abortion fetuses 14-24 weeks of age. This was performed using a Western blot technique. In parallel, ECOD was determined in the same tissue specimens. Of seven different MAbs used MAb PCN 2-13-1/C2 was the only one that immunodetected a cytochrome P-450 band with Western blot analyses of human fetal liver microsomes. This band was consistently detected in all fetal liver specimens studied although the intensity varied among samples. No bands were detected in microsomal preparations from adrenal and renal tissues obtained from the same fetuses. The human adult liver microsomal specimens also contained a MAb PCN 2-13-1/C2 identified cytochrome P-450 band. ECOD activity was detected in all but one of the human fetal livers and varied between 0.22 and 47.5 pmol min-1 mg protein-1, as compared to 113 to 489 pmol min-1 mg protein-1 in human adult livers. In all of the fetuses except one the adrenal ECOD activity (0.63-37.0 pmol min-1 mg protein-1) exceeded that in the liver. The renal ECOD activities were, however, low. The hepatic and adrenal ECOD activities correlated with each other (r = 0.95). Although the ECOD activity is a function of several different P-450s there was also a correlation (r = 0.78) between the ECOD activity and the MAb immunodetected protein band intensity in Western blots of human fetal liver microsomes. The presence of a MAb PCN 2-13-1/C2 identified band in fetal liver microsomes may be indicative of a steroid-dependent effect in fetal life.