POSSIBLE OCCURRENCE OF P450 RELATED TO P450 HFLB IN EXTRAHEPATIC TISSUES OF HUMAN FETUSES AND ITS CONTRIBUTION TO METABOLIC-ACTIVATION OF PROMUTAGENS

P450 HFLb purified from human fetal livers has been shown to be consti tutively expressed in fetal livers. In the present study, the occurren ce of proteins immunochemically related to P450 HFLb in extrahepatic t issues of human fetuses and their contribution to mutagenic activation of promutagens were investigated. The mutagenic activation of aflatox in B1 (AFB1), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3, 4-dimethylimidazo[4,5-f]quinoline (MeIQ) and benzo[a]pyrene were obser ved in human fetal extrahepatic tissues, including adrenal glands, kid neys and lungs, at varying rates. Immunoblot analysis of homogenates o f extrahepatic tissues with antibodies to P450 HFLb revealed the occur rence of proteins immunochemically related to P450 HFLb in adrenal gla nds, kidneys and lungs. Immuno-inhibition studies suggested that in fe tal adrenal gland and kidney, the proteins cross-reactive with antibod ies to P450 HFLb were capable of activating IQ and MeIQ to mutagens.