Antipyrine has been used as a model drug to investigate the effects of liver disease on drug metabolism in man. A prolongation in antipyrine half-life (T(1/2)) was found in patients with liver disease, patients with chronic liver disease showing a greater increase than those with acute, reversible pathology. The most marked prolongation in T(1/2) was found in association with hypoalbuminaemia a...

A mouse mast cell tumor microsomal preparation which catalyzes the incorporation of 35S0., from 3’-phosphoadenosine 5’-phosphosulfate-33S into microsomal heparin has been described. This enzyme preparation is the same preparation that previously has been shown to catalyze the incorporation of sugars into a microsomal glycosaminoglycan related to heparin. It is suggested that polysaccharide poly...

Choline-phosphate cytidylyltransferase (EC 2.7.7.15) activity from 25- and 29-day-foetal rabbit lungs was inhibited in both the cytosolic and the microsomal fractions by preincubation with MgATP. The inhibition of the cytosolic enzyme was greater when measured with added phosphatidylglycerol (PG) than without (78-89% versus 50-55%), whereas the inhibition of the microsomal enzyme did not exhibi...

Cultured Leydig cells exhibited time-dependent decreases in the microsomal cytochrome P-450 enzyme activities, 17 alpha-hydroxylase and C17-20 lyase when maintained under standard culture conditions (95% air, 5% CO2). Inclusion of the hydroxyl radical scavenger dimethyl sulfoxide in the culture medium, or the reduction of oxygen tension from 19 to 1% O2 was effective in preserving these enzyme ...

An enzyme system catalysing the formation of the methylenedioxy bridge at ring A of (S)-canadine [=(S)tetrahydroberberine] from (S)-tetrahydrocolumbamine has been detected in microsomal preparations from different Ranunculaceae and Berberidaceae cell cultures. The cytochrome P-450 enzyme complex has been partly characterized from a protoberberine alkaloid producing Thalictrum tuberosum L. cell ...

We describe the existence of at least two thyroxine 5'-deiodinases in rat liver. They co-fractionate with NADPH-cytochrome c reductase, the marker enzyme for membranes of the endoplasmic reticulum. Subcellular-localization studies of the most active microsomal thyroxine 5'-deiodinase were performed under substrate saturation and at optimal pH 6.8. This enzyme was a Km(app.) of about 3 microM-th...

Administration of dexamethasone to pregnant rats at 19 days gestation increased phosphatidylcholine synthesis (45%) from radioactive choline in type II cells. This enhanced synthesis of phosphatidylcholine was accompanied by an increased conversion of choline phosphate into CDP-choline. Similar results were obtained by incubating organotypic cultures of 19-day-fetal rat lung with cortisol. The ...

Resistance of hypoxic cells to radiation and chemotherapy remains a major limitation to effective therapy of solid tumors. Misonidazole, a 2nitroimidazole analogue, has been studied extensively as a radiosensitizer of hypoxic cells and has been shown to undergo bioreductive metabolism to exert preferential cytotoxicity against hypoxic cells. We have investi gated the effects of misonidazole on ...

One of the major biochemical effects of PCBs is the induction of microsomal enzymes in the liver. Risebrough et al. (1) suggested that PCBs have the capability to induce the activities of microsomal enzymes. Subsequently, Street et al. (2), demonstrated the induction of liver enzymes in rats by PCBs. Since then, a great number of articles have been published on this subject. The enzyme systems ...