Stabilization,solubilization, partial purification and some properties of cytochrome P-450 present in CaCl2-precipitated human placental microsomes

Two forms of a carbon monoxide-binding cytochrome were found to exist in CaCl₂-precipitated microsomal subfractions of human placental homogenates at term. These exhibited absorption maxima at wavelengths of 450 nm and 421–432 nm. Conversion of P-450 to the degradation product could be prevented by resuspension of the microsomes in buffered solutions containing 20% glycerol and 10^?4M dithiothreitol. Solubilization of such resuspended microsomes with sodium cholate could be effected with minimal degradation. The solubilized pigment then could be partially purified by differential fractionation with ammonium sulfate. The partially purified cytochromes did not appear to bind desmethylimpramine but did bind aniline and nicotinamide to yield atypical type II difference spectra with maxima at 435 nm and minima at 416 nm. A type I difference spectrum could be elicited with androstenedione and a spectral dissociation constant (K_S) of 4.7×10^?8M was obtained. Androstenedione also appeared to effectively prevent the binding of carbon monoxide to the cytochrome.     

Effects of antibacterial drugs on the total cholesterol balance of cholesterol-fed mice

Mice were fed a diet containing 1.5% cholesterol, and the total cholesterol balance and the distribution of the consumed sterol among excreta, liver, and carcass were determined, using experimental periods of 9–14 days. It was observed that an average of approximately 12% of the cholesterol was either destroyed or chemically modified. When, however, 1% sulfasuxidine and 0.04% streptomycin were added to the diet, all the sterol “put in” was recovered, within the limits of error of the method. These results were tentatively interpreted to indicate that under the conditions of these experiments, microorganisms of the intestine were primarily responsible for the destruction or modification of the consumed sterol, as observed in the absence of antibacterial drugs.