Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.24.3 (collagenase)
18,340 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In rat liver cells isolated by perfusion in the perfusion in the presence of collagenase, the major portion of cytochrome P-450 is present in the oxidized, nonsubstrate-bound, low spin state. Drug addition to a suspension of liver cells results in the rapid formation of the cytochrome P-450 (Fe3+)-substrate complex which in turn is followed by the appearance of other species with different spectral characteristics before steady state drug monooxygenation is achieved. Cytochrome P-450-linked metabolism of various tested drugs and carcinogenic polycyclic hydrocarbons by isolated rat liver cells is as fast, or faster, as with rat liver microsomes supplemented with a NADPH generating system. Both experimental models respond similarily to phenobarbital or 3-methylcholanthrene pretreatment of the animals and to various of the wellknown inhibitors of drug metabolism. Except with liver cells isolated from fasted, phenobarbital-treated rats, generation of cytosolic NADPH seems sufficient to support optimal drug metabolism even in the absence of added substrates of intermediary metabolism. In isolated liver cells oxidized drug metabolites undergo subsequent metabolic conversion, most often to form the corresponding glucuronides and sulphates. These are readily excreted, whereas non-conjugated products, e.g. free phenols, tend to accumulate intracellularly. Cellular glucuronide formation is strongly inhibited by ethanol-presumably due to an unfavorable effect of the increased NADH/NAD+ ratio on the synthesis of uridine-5'-diphosphoglucuronic acid (UDPGA). In contrast, low concentrations of ethanol have no, or only a slight stimulatory effect on the cytochrome P-450-linked step of drug metabolism and there are indications that the oxidation of low concentrations of ethanol is in fact stimulated by a facilitated reoxidation of cytosolic NADH occuring during drug monooxygenation.
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PMID:Recent studies on cytochrome P-450-linked functions in isolated rat liver cells. 0 26

In vitro addition of rat insulin (200, 400 or 800 muU/ml) to collagenase-isolated pancreatic islets of adult rats diminished glucose (3 mg/ml)-induced insulin release which was correlated with a decrease of the ratio of total NADPH/NADP and inhibition of glucose oxidation via the pentose phosphate shunt (PPS). NADH and NAD levels were not affected. It is suggested that exogenous insulin diminishes the islet total NADPH/NADP ratio by a direct or indirect decrease in PPS activity. However, it is also conceivable that insulin decreases this ratio through another mechanism than PPS. It is possible that inhibition of insulin secretion by exogenous insulin is at least in part due to the decrease of the NADPH/NADP ratio.
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PMID:Pyridine nucleotides in pancreatic islets during inhibition of insulin release by exogenous insulin. 1 90

The influence of the mode of preparation upon some of the characteristics of white adipose tissue plasma membranes and microsomes has been reported. Plasma membrane fractions prepared from mitochondrial pellet were shown to have higher specific activities of (Mg2+ + Na+ + K+)-ATPase than plasma membranes originating in crude microsomes. Isolation of fat cells by collagenase treatment was found to result in a decrease in specific activity of the plasma membrane enzymes; in plasma membranes prepared from isolated fat cells, the specific activity values obtained for (Mg2+ + Na+ +k+)-ATPase and 5'-nucleotidase were only 42% and 6.3% respectively of those obtained in plasma membranes prepared from whole adipose tissue. Purification of whole adipose tissue crude microsomes by hypotonic treatment caused extensive solubilization of the endoplasmic reticulum marker enzymes, NADH oxidase and NADPH cytochrome c reductase. The lability of endoplasmic reticulum marker enzymes, however, was found to be greatly diminished in the preparations from isolated fat cells. The possibility that NADH oxidase and NADPH cytochrome c reductase activities found in the plasma membranes are microsomal enzymes adsorbed by the plasma membranes is discussed. The peptide patterns as well as the NADH oxidase and NADPH cytochrome c reductase activity patterns of plasma membranes and purified microsomes were compared by means of sodium dodecyl sulfate or Triton X-100 polyacrylamide gel electrophoresis.
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PMID:Comparison of plasma membranes and endoplasmic reticulum fractions obtained from whole white adipose tissue and isolated adipocytes. 12 89

Testes of 29-35-day-old rats were separated into seminiferous tubules and interstitial tissue by collagenase treatment and examined by incubation studies with radioactive substrates. The activity of testosterone 5alpha-reductase/g protein in the interstitial tissue was 37 times greater than that in the tubules. The site of formation of 5alpha-reduced C21- and C19-steroids from progesterone was found to be primarily in the interstitial tissue. In the interstitial tissue, testosterone 5alpha-reductase activity, which was stimulated 300-fold by the addition of NADPH, was localized in the microsomal fraction (8,000-105,000 X g precipitate). NADPH was five times as effective a hydrogen donor as NADH when the washed microsomal fraction was the source of the enzyme. The formation of 5alpha-reduced C21- and C19-steroids from pregnenolone and progesterone was demonstrated in the microsomal fraction of interstitial tissue. These results indicate that in 29-35-day-old rat testes, 5alpha-reduction of C19-delta4-3-ketosteroids and the formation of 5alpha-reduced C21- and C19-steroids from pregnenolone take place largely in the microsomes of interstitial tissue.
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PMID:Localization of delta4-5alpha-reductase in immature rat testes. 74

In addition to fibrosis in response to necrosis and inflammation, alcohol may promote fibrogenesis directly, resulting in pericellular, perisinusoidal and perivenular fibrosis, in association with increased collagen mRNA. Acetaldehyde (produced in increased amounts because of the selective induction of cytochrome P450IIE1) stimulates collagen formation from either myofibroblasts, Ito cells or fibroblasts. One postulated mechanism is adduct formation of acetaldehyde with intracellular proteins, possibly stabilized by the NADH generated upon ethanol oxidation. The latter also increases lactate which might inhibit proline oxidase activity and increase available proline. During the initial stage of alcohol consumption, collagenase activity is increased, in keeping with enhanced collagen production. In later stages, however, there is a secondary decrease of collagenase activity; its deficiency relative to synthesis may also promote collagen deposition. In the early stage of alcohol induced fibrosis, collagens type I and type III accumulate, whereas later, type I predominates. Both can be formed in vitro by Ito cells, but cultured hepatocytes produce mainly type III. Immunohistochemical techniques revealed the deposition of type III procollagen in the extrahepatic collagen fibrils. Its degradation, as well as its enhanced synthesis, contribute to the appearance of procollagen III peptides in the blood. Their measurement by Fab fragments of the antibody is useful to assess the degree of fibrosis and to detect perivenular fibrosis, a precirrhotic lesion. In the baboon model, polyunsaturated lecithin was found to be effective in opposing alcohol-induced fibrosis.
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PMID:Alcohol and fibrogenesis. 184 59

A method for measurement of glutamate dehydrogenase (GDH) activity in single renal tubules was employed to determine the distribution and regulation of GDH in tubule segments. Fresh microdissected tubules from collagenase-treated kidneys were permeabilized by hyposmotic shock and freezing. The rate of conversion of alpha-ketoglutarate, NH4+, and NADH to glutamate and NAD was measured at 37 degrees C fluorometrically. Very high activities were found in proximal tubule segments (150-210 pmol.min-1.mm tubule length-1), intermediate values (40-90 pmol.min-1.mm-1) in distal convoluted tubules, cortical thick ascending limbs, connecting tubules, medullary thick ascending limbs, and lower values (5-30 pmol.min-1.mm-1) in cortical collecting ducts, inner medullary collecting ducts, outer medullary collecting ducts, outer medullary thin limbs, and inner medullary thin limbs. To determine the effects of acid-base loading on GDH activity, 0.28 M NH4Cl (acid) or 0.28 M NaHCO3 (alkali) was added to the animals' drinking water for 7 days. Acid intake by the rats increased GDH activity in S1 and S2 proximal tubules by threefold, with no effect in other segments, including S3 proximal tubules. Alkali intake decreased GDH activity in the S3 proximal tubule by 40%, with no effect in other segments. We conclude that GDH activities are highest in proximal tubule segments and are regulated only in proximal tubule segments. Thus the results are consistent with the view that the proximal tubule is the chief site of the regulated production of ammonium in the kidney.
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PMID:Glutamate dehydrogenase activities in microdissected rat nephron segments: effects of acid-base loading. 237 92

The viability of adult Onchocerca volvulus and the effect of 12 known anthelmintic compounds on the parasites have been evaluated in an in vitro culture system. Three different parameters, a colorimetric assay, using NADH-dependent reduction of a tetrazolium salt to dark blue formazan by living adult worms, motility indices of male worms and lactate excretion of female worms were used to determine worm viability. The experiments showed that over a short term period of six days the viability of the worms did not decline significantly. The use of males isolated by dissection of whole nodules for the evaluation of drug effects in vitro is preferable to collagenase isolated worms. Mel W, milbemycin a and d, ivermectin, levamisole, CGP 6140 and, to a lesser extent, suramin immobilized male worms or significantly reduced the motility indices at a concentration of 10 microM. The tetrazolium reduction by male worms was not affected by levamisole, whereas the other active compounds demonstrated significant inhibitory effects. Diethylcarbamazine, mebendazole, flubendazole, metrifonate and CGP 20376 had no significant effect on male viability. Comparable activity was seen with the intact female worms isolated by collagenase digestion. Mel W, the milbemycins and ivermectin significantly inhibited tetrazolium reduction, whereas suramin and the other compounds had only slight or no inhibitory effects on female O. volvulus. Although one still has to aim at an improvement of the culture conditions, the in vitro test system using adult O. volvulus provides a basis for further research on potential antifilarial compounds.
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PMID:In vitro assessment of the activity of anthelmintic compounds on adults of Onchocerca volvulus. 237 12

The antihyperglycemic agent, metformin (dimethylbiguanide), inhibits hepatic gluconeogenesis. To investigate the mechanism involved, glucose production from collagenase-isolated hepatocytes of starved rats was determined after 1 hr incubations with different substrates. In the absence of insulin, glucose production from 10(-2) M lactate-10(-3) M pyruvate, 10(-2)M M alanine, 10(-2) M glutamine and 5 x 10(-3) M glycerol was decreased (35-78%) by high concentrations (10(-2) and 10(-3) M) of metformin. Lower concentrations of metformin were not effective in the absence of insulin, but a therapeutic concentration (10(-5) M) of metformin acted synergistically with insulin (10(-8) M) to suppress gluconeogenesis from each of the substrates by an additional 10-14% compared with insulin (10(-8) M) alone. The synergistic antigluconeogenic effect of metformin (10(-5) M) with insulin (10(-8) M) was achieved without alteration of the contents of NADH and NAD+ in digitonin-separated cytosolic and mitochondrial-rich hepatocyte fractions. Mitochondrial ATP was also unaltered by the metformin (10(-5) M)-insulin (10(-8) M) combination. However, the antigluconeogenic effect of 10(-2) M metformin alone was associated with an increased (by 109%) mitochondrial NADH:NAD+ ratio. Thus reduced gluconeogenesis by high concentrations of metformin (e.g. 10(-2) M) may involve changes of redox state. However, therapeutic concentrations of metformin (e.g. 10(-5) M) potentiate the antigluconeogenic effect of insulin to a similar extent from a range of substrates, without altering energy status or redox state.
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PMID:Inhibition of hepatic gluconeogenesis by metformin. Synergism with insulin. 305 29

Liver microsomes were isolated by calcium aggregation, and isolated hepatocytes from male Wistar rats were prepared according to a two-step Ca++-free collagenase perfusion method. With the hepatocytes maximal inhibition of glucuronidation (about 40%) was reached at 10 mM ethanol after incubation at 37 degrees C for 60 min. UDP-glucuronic acid concentration and energy charge in the hepatocytes also did decrease maximally (about 90 and 50%, respectively) and the amount of UDP-glucose was tripled in the presence of 10 mM and higher concentrations of ethanol. The alcohol dehydrogenase inhibitor 4-methylpyrazole abolished ethanol-induced inhibition of morphine glucuronidation in the hepatocytes. Acetaldehyde (250-50 microM) and the pH decrease induced by ethanol did not reduce morphine-3-glucuronide formation by the cells. Cellular uptake of morphine and excretion of morphine metabolites were similar in the absence and presence of ethanol. Ethanol (60 mM) did not affect the glucuronidation of morphine (1.7 mM added) during a 30-min incubation at 37 degrees C with the microsomes (UDP-glucuronic acid, 5 mM). When the concentration of UDP-glucuronic acid in the microsomes was lowered from 1 to 0.1 mM, the decrease in morphine-3-glucuronide formation was similar to that observed in cells. The data indicate that the inhibition by ethanol of morphine glucuronidation was due to decreased levels of UDP-glucuronic acid. The mechanism is likely to be inhibition of UDP-glucose dehydrogenase activity by ethanol from increased intracellular NADH/NAD ratio accompanying ethanol oxidation.
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PMID:Mechanisms behind the inhibitory effect of ethanol on the conjugation of morphine in rat hepatocytes. 379 46

Localization of NAD+-dependent (type I) 15-hydroxyprostaglandin dehydrogenase (15PGDH) in the rat kidney was examined using an ultramicro assay of the enzyme activity based on the enzymatic cycling method. The enzyme activities during first 3 weeks of age were 30- to 40-fold higher than the adult and rapidly decreased by 4th week. 15PGDH activities measured with either PGE2 or PGF2 alpha as a substrate were five times higher in slices from midcortical or juxtamedullary layers than in slices from the superficial cortex of 3 week-old rat kidney. Little activity was found in inner medulla and papilla. When the enzyme activity was assayed using isolated nephron segments dissected from collagenase treated slices of 3 week-old rat kidneys, the activity was localized only in the proximal convoluted and straight tubules with either PGs (PGE2: 1.75 +/- 0.25 in PCT, 7.70 +/- 1.19 in PST, and PGF2 alpha: 1.63 +/- 0.39, 6.18 +/- 1.52 pmoles NADH/mm/40 min). The kinetic analysis for renal 15PGDH of 3 week-old rats revealed that Km for PGE2 (8.4 microM) was lower than that for PGF2 alpha (22.6 microM) with constant NAD+, while Vmax for both was similar. In contrast, both Km and Vmax for NAD+ were identical with either PGs. These data suggest that the rate-limiting factor of type I 15PGDH is the concentration of prostaglandins in the kidney rather than the concentration of NAD+.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Localization and properties of NAD+-dependent 15-hydroxyprostaglandin dehydrogenase activity in the rat kidney. 403 73


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