The mechanisms responsible for gonadotropin-induced testicular desensitization were analyzed by direct assay of androgen biosynthetic enzymes and cytochrome P-450 in microsomes and cytosol from testes of adult male rats. Animals were treated with single subcutaneous doses of human chorionic gonadotropin (hCG) (2 and 10 pg) to induce a post-stimulation decrease in testosterone production, previo...

The enzyme system in liver microsomes which catalyzes the w-hydroxylation of fatty acids in the presence of molecular oxygen and a reduced pyridine nucleotide has been solubilized and resolved into fractions containing cytochrome P-450, a cytochrome P-450 reductase, and a heat-stable factor. The apparent K, values of TPNH and DPNH are 2.0 x 10m5 M and 6.3 X 10e4 M, respectively. As a further in...

Antibodies to cytochrome P-450 isozyme 3a, the ethanol-inducible isozyme in rabbit liver, were used to determine the role of this enzyme in the microsomal oxidation of alcohols and the p-hydroxylation of aniline. P-450 isozymes, 2, 3b, 3c, 4, and 6 did not crossreact with anti-3a IgG as judged by Ouchterlony double diffusion, and radioimmunoassays indicated a crossreactivity of less than 1%. Gr...

1. A new microsomal preparation, obtained from whole houseflies is described in terms of its cytochrome P-450 content and its hydroxylating activity. 2. Microsomes prepared from whole-fly brei, obtained with the aid of a mortar (a procedure that avoids the destruction of sarcosomes), contain 0.265nmol of cytochrome P-450 and hydroxylate naphthalene at a rate of 28.5nmol/mg of microsomal protein...

A potent inhibitor of microsomal mixed-function oxidation reactions in insects had previously been isolated and partially purified from the gut contents of Prodenia eridania and shown to be associated with proteinase activity. Incubation of rat liver microsomal fraction with low concentrations of this inhibitor led to solubilization of NADPH-cytochrome c reductase, which was paralleled by the i...

Polyclonal antibodies were prepared against NADPH-cytochrome P-450 reductase purified from Jerusalem artichoke. These antibodies inhibited efficiently the NADPH-cytochrome c reductase activity of the purified enzyme, as well as of Jerusalem artichoke microsomes. Likewise, microsomal NADPH-dependent cytochrome P-450 mono-oxygenases (cinnamate and laurate hydroxylases) were efficiently inhibited....

These findings could be interpreted as implying that the enhancement by carcinogens in vitro of hamster hepatic microsomal biphenyl 2-hydroxylase (McPherson ‘et al., 19746) is mediated through an effect on the microsomal membrane rather than via direct specific conformational modification of the biphenyl 2-hydroxylase enzyme itself. In an attempt to differentiate between the soluble and microso...

A microsomal fraction isolated from the shoots of 3- to 4-day-old, dark-grown, grain sorghum (Sorghum bicolor cv. Funk G 522 DR) seedlings was characterized. The preparations had a cytochrome P-450 content that varied from approximately 90 to 150 pmol P-450/mg protein with cytochrome P-420 varying from 0 to 3% of the P-450 content. Type I difference spectra were formed with cinnamic acid and me...

The relevance of the stimulation of 5-aminolaevulinate synthetase to the accumulation of cytochrome P-450 after administration of drugs was examined in rats treated with phenylbutazone and with 3,5-diethoxycarbonyl-1,4-dihydrocollidine. 3,5-Diethoxycarbonyl-1,4-dihydrocollidine alone stimulated 5-aminolaevulinate synthetase without increasing the concentration of cytochrome P-450, whereas pheny...

Protection afforded by trialkyl phosphorothionates against the lung injury caused by trialkyl phosphorothiolates probably results from the inhibition by the P = S moiety of the thionates, of one or more pulmonary cytochrome P-450 isozymes. The aromatic hydrocarbons p-xylene and pseudocumene also protect against this injury and inhibit some P-450 isozymes, but by a different mechanism. OOS-Trime...