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)

We studied the possible relationships between the functional status of the beta-cell and activities or mRNA contents of enzymes involved in the catabolism of glucose. Three different in vitro models with attenuated insulin response were used: rat islets cultured at a low glucose concentration, rat islets incubated in vitro with streptozocin, and fetal rat islets. The fetal and streptozocin-administered islets were compared with adult islets cultured in RPMI-1640 containing 11 mM glucose, and the effects of the in vitro glucose concentrations (3.3, 11, and 28 mM) were assessed on adult islets only. Cellular mRNA levels for the mitochondrial DNA-encoded cytochrome b and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were determined by Northern-blot analysis. Enzymatic activities of high-Km (glucokinase) and low-Km (hexokinase) glucose-phosphorylating enzymes and succinate-cytochrome c reductase were also determined. Islets cultured at 3.3 mM glucose displayed a decreased activity of glucokinase compared with islets cultured at 28 mM glucose (23.3 +/- 12%), whereas there was no difference in hexokinase activity or the level of GAPDH mRNA. The activity of succinate-cytochrome c reductase was similar in islets cultured at the different glucose concentrations. The level of cytochrome b mRNA increased at 28 mM glucose compared with islets cultured at 11 mM glucose (140 +/- 14%). Islets incubated with streptozocin and subsequently cultured for 7 days at 11 mM glucose exhibited a decreased level of cytochrome b mRNA (65 +/- 5%) and no differences in the activities of glucokinase, hexokinase, succinate-cytochrome c reductase, or the level of GAPDH mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Exhibition of specific alterations in activities and mRNA levels of rat islet glycolytic and mitochondrial enzymes in three different in vitro model systems for attenuated insulin release. 164 83

A film test for the rapid detection of plasma/serum 3-hydroxybutyrate (3-OHB) has been developed. The film contains NAD, nitro blue tetrazolium, 3-OHB dehydrogenase, and diaphorase, and the surface is coated with modified biomembrane and can detect 50-1500 microM 3-OHB within 2-3 min. One drop or 50 microliters of plasma/serum or blood is applied to the film, and the violet color is read via reflectance meter after 2 min. Plasma/serum samples greater than 1500 microM 3-OHB can be measured by dilution with saline. In blood with 40% hematocrit, the color developed is 50% less than with plasma/serum, and this was adjusted in the reflectance meter. A good correlation (r = 0.99) was observed between results with automated and film methods and between visual methods and reflectance meter. In insulin-dependent diabetes mellitus, all 3 subjects with positive ketonuria (+ +), 8 of 12 subjects with mild ketonuria (+), and 7 of 25 subjects without ketonuria exhibited elevation of 3-OHB in blood greater than 200 microM. The results indicate that 3-OHB film is valuable not only in the emergency room for the differential diagnosis between ketoacidotic and nonketotic hypersomolar coma but also as a marker for insulin dependency, energy dependency on fatty acid compared with glucose, and metabolic control of diabetes.
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PMID:Development of stable film test for rapid estimation of blood or plasma 3-hydroxybutyrate. 235 Oct 30

Esters of carboxylic acids are permeable to cells and once inside the cell are hydrolyzed to carboxylic acids. Methyl and ethyl esters of succinate and other citric acid cycle intermediates were tested to find out whether they are insulin secretagogues. Monomethyl succinate stimulated insulin release from pancreatic islets in a concentration-dependent manner with maximal release attained at a concentration of 10 mM. Dimethyl succinate (10 mM) was as effective as monomethyl succinate, but pyruvate methyl ester, monoethyl succinate, and dimethyl fumarate were ineffective as primary secretagogues. However, dimethyl fumarate potentiated both leucine- and leucine-plus-glutamine-induced insulin release. Glucose, leucine, leucine plus glutamine, and monomethyl succinate increased inositol tris-, bis- and monophosphate formation in pancreatic islets and antimycin A inhibited this formation. Since mitochondrial metabolism is probably essential for glucose-induced insulin release and the metabolism of succinate and leucine (without or with glutamine) involves mitochondrial respiration exclusively, these results might indicate that mitochondrial metabolism generates conditions or factors that are transmitted to the cytosol to increase inositol trisphosphate formation and thus calcium mobilization and insulin release. Since succinate is believed to enter metabolism at site II of the mitochondrial respiratory chain, it is interesting that rotenone, an inhibitor of NADH dehydrogenase and site I of the respiratory chain, was a potent inhibitor of monomethyl succinate-induced insulin released. Rotenone also inhibited leucine (plus or minus glutamine)-induced insulin release. These results indicate that beta cell metabolism of monomethyl succinate and leucine, like glucose, influences dehydrogenases that produce NADH.
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PMID:Effect of esters of succinic acid and other citric acid cycle intermediates on insulin release and inositol phosphate formation by pancreatic islets. 264 27

Therapy with enzyme inducing drugs may improve glycemic control in patients with non-insulin-dependent diabetes mellitus. We evaluated the role of a mixed function oxidase system on glucose metabolism with an animal model. Rats were treated with an inducer (phenobarbital), an inhibitor (cimetidine) and a hepatotoxin (carbon tetrachloride) for a week to cause alterations in the liver. The mixed function oxidase system was assayed by determination of the cytochrome P-450 content and NADPH cytochrome c reductase in liver. Carbohydrate metabolism was evaluated by determining blood glucose, enzymes associated with glucose phosphorylation in the liver (glucokinase, hexokinase), glucose storage as glycogen and enzymatic delivery, glucose-6-phosphatase, and peripheral tissue by determining phosphorylating enzyme (hexokinase) and a key glycolytic enzyme (pyruvate kinase) and glycogen content in muscles. The therapy with the inducer enhanced glucose utilization in liver and storage in muscles. The inhibitor decreased the mixed function oxidase system, reduced glucose phosphorylating, but not gluconeogenetic enzymes, in the liver and increased glycolysis in muscles. Carbon tetrachloride, a hepatotoxin, impaired mixed function oxidase, glucose phosphorylating and delivering enzyme activity in liver, reduced blood glucose and caused glycogen accumulation in muscles. The function of liver microsomal enzyme system seems to be closely related to enzymatic glucose metabolism in the liver and muscles.
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PMID:Hepatic mixed function oxidase system and enzymatic glucose metabolism in rats. 304 Mar 22

A cloned fetal Syrian hamster lung epithelial cell line (M3E3/C3) was used to compare the influence of two different culture conditions on the degree of cellular differentiation and susceptibility of the cells to undergo malignant transformation by a precarcinogen, benzo(a)pyrene. Conventional conditions consisted of growth medium containing Roswell Park Memorial Institute Medium 1640, pyruvate, and fetal bovine serum and a substratum of plastic. Complex conditions comprised the growth medium supplemented with insulin, hydrocortisone, estradiol, epidermal growth factor, transferrin, and cholera toxin and a substratum of collagen gel. Under the complex culture conditions, there was extensive development of endoplasmic reticulum and Golgi vesicles, whereas under conventional conditions these organelles were only minimally developed. This was correlated with 1.5-1.8 times enhancement of ethoxycoumarin deethylase and reduced nicotinamide adenine dinucleotide phosphate-dependent cytochrome c reductase activities. Decomposition of added benz(a)anthracene into water-soluble compounds increased with the period of incubation and reached about 40% of initial benz(a)anthracene (50 micrograms/10 ml/flask) at 48 h under the complex conditions, whereas under the conventional conditions only less than 4% decomposition occurred. Benzo(a)pyrene in the dose range 2-8 micrograms/ml was strongly cytotoxic and caused significant anchorage independent transformation only under complex culture conditions. Transformed cells produced tumors in two of four hamsters during 8 months following s.c. injection within 48 h of birth. These results suggest that the complex culture conditions predisposed the cloned fetal epithelial cells to malignant transformation by benzo(a)pyrene through stimulation of cellular differentiation and development of enzyme systems capable of activating it metabolically.
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PMID:Predisposition of cloned fetal hamster lung epithelial cells to transformation by a precarcinogen, benzo(a)pyrene, using growth hormone supplementation and collagen gel substratum. 380 97

The NMuMG cell line derived from normal mouse mammary epithelial cells was tested for responsiveness to hormones. The hormones studied included insulin, glucocorticoids (cortisol and dexamethasone), and prolactin. In addition to membrane bound insulin receptors and prolactin receptors, the cells had 2 X 10(4) cytoplasmic glucocorticoid receptors per cell. Morphological changes were observed in response to hormones. Clusters of cells appeared with greatly increased diameter, and the number of cells per plate was reduced. The rate of DNA synthesis, corrected by cell number, indicates that cell division, and hence cell turnover, was increased by the combination of all three hormones. Insulin greatly enhanced protein synthesis, but glucocorticoid and prolactin did not further increase the rate. The combination of three hormones produced a change in the synthesis of histones, consistent with the increase in cell turnover. There were substantial responses of enzyme activities to hormonal treatment of the cells. Insulin by itself induced a doubling of the activity of glyceraldehyde phosphate dehydrogenase and perhaps a modest increase in NADH-cytochrome c reductase. Lactose synthetase activity showed a three- to fourfold induction of both A and B subunits of the enzyme when the cells were treated with insulin, glucocorticoid, and prolactin, and the effect of the latter two hormones was shown to be additional to that of insulin.
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PMID:A test for hormonal responsiveness in a mammary epithelial cell line, NMuMg. 629 Mar 75

Mammary explants from pregnant rats can be induced in regard to casein synthesis and alpha-lactalbumin activity when cultured in the presence of hydrocortisone, prolactin and levels of insulin approaching physiological concentrations. No detectable induction occurs in the absence of insulin. Although epidermal growth factor and multiplication stimulating activity, in the presence of hydrocortisone, can maintain the initial level of NADH-cytochrome c reductase as well as insulin, neither can substitute effectively for insulin in the induction of the milk proteins. Proinsulin, nerve growth factor, platelet-derived growth factor and fibroblast growth factor are also ineffective substitutes for insulin in this regard. Whereas prolonged tissue exposure to multiplication stimulating activity, hydrocortisone and prolactin does not result in induction of alpha-lactalbumin activity, subsequent addition of insulin leads to prompt response. The results suggest that the ability of insulin to function as a unique, essential factor in the induction of rat milk proteins is independent of its cell-maintenance activity. Thus, in addition to its well established functions in metabolic processes, insulin appears to play a vital role in certain developmental processes.
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PMID:A unique and essential role for insulin in the phenotypic expression of rat mammary epithelial cells unrelated to its function in cell maintenance. 635 73

The activity of NAD-linked alpha-glycerol-3-phosphate dehydrogenase (NAD-G3PDH; EC 1.1.1.8) was depressed by 35% when the thyroid hormone 3,3',5-triiodo-L-thyronine (20 micrograms/liter) was added to the serum-free, hormonally supplemented medium of cultured neonatal rat heart cells. The degree of depression was greater (65%) when the medium contained normal serum levels of hydrocortisone and insulin. There is a dramatic inverse dose-response relationship between triiodothyronine levels and NAD-G3PDH activity. The classic elevation by thyroid hormones of the FAD-linked alpha-glycerol-3-phosphate dehydrogenase (FAD-G3PD; EC 1.1.99.5) was observed concurrently. The medium-glucose depletion rate in triiodothyronine-free cells was depressed 32% through 11 days-in-culture, indicating reduced glycolytic activity. The activities of nine other metabolically important enzymes which were measured during this study, including hexokinase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, phosphofructokinase, pyruvate kinase, malate dehydrogenase, NAD-isocitrate dehydrogenase, NADH cytochrome c reductase, and succinic cytochrome c reductase, did not respond to varying triiodothyronine concentrations.
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PMID:Triiodothyronine depresses the NAD-linked glycerol-3-phosphate dehydrogenase activity of cultured neonatal rat heart cells. 669 42

The differentiative functions, lactose synthetase activity and casein synthesis, can be induced in mammary gland explants from intact mice when insulin, cortisol, and PRL are present in the medium. By contrast, the tissue from mice castrated for 1--2 months does not differentiate in vitro. Explants from these ovariectomized animals retain their sensitivity toward insulin, as evidenced by the ability of this hormone to stimulate DNA synthesis, alpha-aminoisobutyric acid accumulation, and glucose-6-phosphate/gluconate-6-phosphate dehydrogenase activities. This tissue also remains sensitive to cortisol, as evidenced by the ability of this steroid to stimulate NADH-cytochrome c reductase activity. However, the tissue from ovariectomized mice has lost biological responsiveness to PRL. Such insensitivity may be due to a deficiency of PRL receptors, which are reduced in the glands from castrated mice to 20--25% of control values. However, a second defect between the receptor and the genome is also likely, since PRL unresponsiveness is still present in the tissue of ovariectomized animals whose mammary PRL-binding has been partially maintained by elevating serum PRL levels with a pituitary transplant. Therefore, this system may be useful for the study of cellular processes related to PRL action beyond the receptor level.
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PMID:Loss of differentiative potential of the mammary gland in ovariectomized mice: identification of a biochemical lesion. 678 89

The activity of hepatic NADPH cytochrome c reductase, an enzyme important in drug and steroid metabolism, increases rapidly during the perinatal period in rats. However, the regulation of this increase is not well understood. To investigate the role of hormones in the development of NADPH cytochrome c reductase activity, fetal rat livers in organ culture were used in the present study. Explants from 20-day-old fetal rat liver could be maintained for up to 96 h in a serum-free medium with or without added hormones. When the explants were exposed to 50 nM L-T3 for 72 h, they had 74% greater NADPH cytochrome c reductase activity than controls. In contrast, 1 microM hydrocortisone (HC) stimulated reductase activity by only 20%. However, when T3 was added with HC there was a synergistic effect, resulting in a 167% elevation in NADPh cytochrome c reductase activity. The response to T3 plus HC was detectable after 24 h and maximal after 72 h. Control activity rose slightly during the first 48 h in culture and was stable thereafter. Stimulation of reductase activity by T3 was detectable at 0.1 nM, half maximal at 2 nM, and maximal between 10 nM and 100 nM. T4 also stimulated NADPh cytochrome c reductase activity in explants but was only 3-4% as potent as T3. The effect of steroids was specific for glucocorticoids. Neither glucagon nor insulin had any measurable effect on reductase activity. Electron micrographs revealed that hepatic ultrastructure was well preserved for at least 72 h of incubation in the presence or absence of hormones. The data suggest, therefore, that the normal perinatal development of hepatic NADPH cytochrome c reductase activity in rats is regulated at least in part by thyroid hormones acting synergistically with glucocorticoids.
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PMID:Synergistic regulation of fetal rat liver nicotinamide adenine dinucleotide phosphate (reduced form) cytochrome c reductase activity: effects of L-triiodothyronine and hydrocortisone. 680 20


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