RT Journal Article
SR Electronic
T1 STUDIES ON HUMAN PLACENTAL CARBON MONOXIDE-BINDING CYTOCHROMES
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 79
OP 86
VO 2
IS 1
A1 M. R. JUCHAU
A1 P. K. ZACHARIAH
A1 J. COLSON
A1 K. G. SYMMS
A1 J. KRASNER
A1 S. J. YAFFE
YR 1974
UL http://dmd.aspetjournals.org/content/2/1/79.abstract
AB Studies with marker enzymes, difference spectra, and electron microscopy have confirmed the presence of a carbon monoxide-binding cytochrome in both the mitochondria and endoplasmic reticulum of human placentas. The position of the absorption maximum of the CO complex (450-form) was dependent on the method of spectral analysis utilized but was independent of aryl hydrocarbon hydroxylase activity and gestational age. An altered form of the cytochrome ("428-form) exhibited absorption maxima which varied between 421 and 434 nm. The rate of conversion of the 450-form to the "428"-form could be retarded markedly if buffered solutions containing 10-4 M dithiothreitol and 20% glycerol were utilized for the resuspension of placental particulate fractions. The cytochrome could be solubilized with sodium cholate and partially purified without significant conversion to the "428"-form. The pigment was detectable both at term and during the first two trimesters of pregnancy. Preliminary observations indicated a possible inverse correlation between the cytochrome P-450 content and aryl hydrocarbon hydroxylase activities observed in placental particulate fractions. No difference in the positions of the absorption maxima could be observed in placentas with very high vs. very low aryl hydrocarbon hydroxylase activities. Differences between rat hepatic microsomal cytochrome P-450 and the placental cytochrome were noted with respect to ethyl isocyanide-, n-octylamine-, and CO-binding spectra, rates of temperature-dependent conversion to the "428"-form, and the effects of p-chloromecuribenzoate on the CO difference spectra. Copyright © 1974 by The American Society for Pharmacology and Experimental Therapeutics