Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.6.99.3 (diaphorase)
 5,903 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

When incubated with 3H-astemizole, a potent antagonist of H1 receptor, cultured rat hepatocytes, which do not express specific receptors for this ligand, avidly take up 3H-label proportionally to the drug concentration. HPLC analysis indicates that at 10 ng 3H-astemizole/ml, cells almost entirely deplete the culture medium of the drug within 4 hr of incubation. At 37 degrees, astemizole is metabolized and released into the culture medium mainly under the form of glucuronoconjugated metabolites. Differential centrifugation of homogenates from hepatocytes incubated with 3H-astemizole indicates that astemizole and unconjugated metabolites are found in the particulate fraction, whereas astemizole and conjugated metabolites are present in the cytosol. Isopycnic centrifugation on sucrose gradient shows that the major part of the 3H-label in the particulate fraction distributes like phospholipids and NADPH cytochrome c reductase, suggesting an association with membranes and, in particular, with the endoplasmic reticulum. Chloroquine, a drug accumulating within lysosomes and acidic endosomes, decreases the uptake of 3H-astemizole by hepatocytes and induces, during isopycnic centrifugation of a particulate fraction, a shift of the 3H-label towards lower densities where it closely accompanies cathepsin B. This suggests that a minor part of astemizole accumulated in the hepatocytes could be trapped within lysosomes. These results could support the hypothesis that aspecific binding of astemizole to cellular membranes and, to a lesser extent, trapping in lysosomes could play a role in the pharmacokinetics of the drug.
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PMID:Uptake, subcellular distribution and biotransformation of 3H-labelled astemizole in cultured rat hepatocytes. 312 Jul 32

Rat kidneys were preserved by initial washing and cooling perfusion, followed by cold storage at 6 degrees C for 24, 48, 72 and 96 hours, in two different media: Sacks (hyperosmolar electrolytic solution of intracellular type) and Plasmagel (gelation solution 4%). Evidence was found of DPNH-diaphorase, lactate dehydrogenase (LDH), leucylaminopeptidase (LAP) and adenosine-triphosphatase (ATPase) (pH 9.4) activities. Histoenzymological determination showed various levels of enzymatic activities in different segments of the nephron, levels relatively well maintained during storage, even at 72 and 96 hours. At the same time, cathepsin B and D and neutral proteinase activities were determined as parameters of maintained cellular enzymatic activity; different aspects were observed with the two preservation media used.
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PMID:Morphological aspects of the rat kidney preserved by cold storage. IV. Histoenzymological changes. V. Endopeptidase activity. 623 99

With the aim of studying the mechanism behind the effect of estramustine in the treatment of prostatic carcinoma, the intracellular fate of the drug has been investigated in rat ventral prostate in vitro. Minced tissue was incubated with [3H] estramustine under different conditions, homogenized, and submitted to isopycnic centrifugation on a sucrose gradient using the recently introduced vertical tube rotor. The subcellular localization of the drug was determined by comparison between the distribution of radioactivity in the gradient fractions and the activities of a number of marker enzymes. No metabolism of estramustine occurred as judged by thin-layer chromatography. After incubation of the minced prostate tissue for 1 hour at 30 degrees C with 0.15 microM of [3H] estramustine, most of the drug was recovered in the cytosol fractions which also contained the highest concentrations of the estramustine-binding protein. However, after incubation with 220 microM of estramustine, most drug equilibrated in heavier fractions with high concentrations of N-acetyl-beta-glucosaminidase and cathepsin B, marker enzymes for the lysosomes as well as NADPH:cytochrome c reductase, marker enzyme for the endoplasmic reticulum. Extending the incubation time and increasing the temperature reduced the amount of estramustine equilibrating in the heavy fractions and concomitantly increased the portion localized in the cytosol. During all incubation conditions, very little drug seemed to accumulate in the nuclei since the drug distribution was completely different from that of DNA. This suggests that effects other than interaction with nuclear DNA might be of importance for the cytotoxic effect of estramustine.
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PMID:Intracellular localization of estramustine in rat ventral prostate in vitro. 679 11

Proximal tubules were isolated in highly pure form from rabbit cortices by a mechanical procedure that is known to preserve the structural and metabolic aspects of the tubular cells. Postnuclear supernates prepared from the isolated tubules were subjects to isopycnic centrifugation in linear sucrose gradients. The enzyme activities associated with the plasma membrane (gamma-glutamyl transpeptidase, amino-peptidase M, alkaline phosphatase, Na-K-ATPase, and phosphodiesterase I) exhibited sharp unimodal frequency-density profiles with a median density near 1.16 g/ml, which shifted to a heavier density when treated with digitonin. The lysosomal enzymes, N-acetyl-beta-glucosaminidase, alpha-mannosidase, and cathepsin B, and the peroxisomal enzyme catalase exhibited particle-associated activity near a density of 1.22 g/ml. Disruption of these particles by freezing and thawing resulted in these activities appearing in the rho = 1.10 g/ml region of the gradient where the soluble cytosolic enzyme, phosphoglucomutase, exhibited activity. Cytochrome oxidase activity typical of mitochondria gave a sharp unimodal profile at rho = 1.18 g/ml. Microsomal glucose-6-phosphatase and NADPH: cytochrome c reductase activities gave median densities near 1.16 g/ml, which did not change after incubation with digitonin. Galactosyl transferase activity gave a skewed profile at rho = 1.16 g/ml and showed a slight shift to heavier density after digitonin. This study of the enzymatic activities and density gradient distribution of the components of the proximal tubule cells provides the methodology for the further study of the cellular processing of endogenous and exogenous substances by this vital cell type.
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PMID:Analytical cell fractionation of isolated rabbit renal proximal tubules. 730 Jan 16