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:3.1.3.5 (5'-nucleotidase)
3,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glucagon receptor levels, glucagon-stimulated and other forms of adenylyl cyclase activity, and regulatory component activity of adenylyl cyclase were determined in hepatic plasma membranes of rats administered streptozotocin without and with insulin to produce varying degrees of hyperglycemia. Receptor levels were assayed by direct binding of the specific probe [125I-Tyr10]-iodoglucagon; regulatory component activity was assayed by the capacity to reconstitute stimulatory regulation in deficient membranes from cyc- S49 murine lymphoma cells. In rats given 150 mg streptozotocin, glucagon stimulation of adenylyl cyclase as well as basal, sodium fluoride, 5' guanylylimidodiphosphate [GMP-P(NH)P] and Mn-dependent activities were reduced 50%, glucagon receptor levels but not affinity were reduced 67%, and regulatory component activity was decreased 50%. In addition, alpha 1-adrenergic receptors and 5'-nucleotidase were similarly reduced in diabetes. However, specific ouabain-inhibitable Na+, K+, ATPase activity was not altered by streptozotocin treatment. The streptozotocin-induced changes were noted within 24 h and became maximal by 120 h after its administration. All of these decreases were partially reversed by in vivo insulin treatment. DNA, cytochrome c oxidase, glucose-6-phosphatase, and N-acetyl-beta-glucosaminidase content in hepatic plasma membrane preparations were not substantially different in diabetic as compared with control animals. The data demonstrate that glucagon-mediated regulation of cyclic AMP formation is deranged in insulin deficiency owing to a combined decrease in receptors, derangement of the coupling mechanism intervening between receptor and adenylyl cyclase, and possibly, an altered basal effector system. Some of these changes appear to reflect a "desensitization-like" phenomenon which may or may not be attributable to the hyperglucagonemia of diabetes mellitus. There also appears to be a concurrent generalized decrease in several but not all plasma membrane receptor and enzymatic proteins. This may be the result of a number of processes among which is the accelerated proteolysis of uncontrolled diabetes.
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PMID:Glucagon-stimulable adenylyl cyclase in rat liver. The impact of streptozotocin-induced diabetes mellitus. 632 32

The mechanism of insulin action on glucose transport in rat hearts was studied. The glucose transport activity was determined after reconstitution into egg lecithin liposomes. Isolated rat hearts were perfused in the presence or absence of insulin and homogenized. The homogenate was fractionated by differential and sucrose density gradient centrifugations. Two subcellular fractions, designated as Fractions P-5 and P-6, contained glucose transport activity. Both fractions were enriched with 5'-nucleotidase (commonly known as a plasma membrane marker) and UDP-Gal:N-acetylglucosamine galactosyltransferase (known as a Golgi marker). However, only Fraction P-5 was concentrated with the insulin receptor and ouabain-sensitive p-nitrophenylphosphatase (both plasma membrane markers). The sedimentation properties of the glucose transport activity in Fraction P-6 were considerably different from those of galactosyltransferase. Insulin added to the heart before homogenization increased the glucose transport activity in Fraction P-5 approximately 1.6-fold while decreasing the activity in Fraction P-6 to approximately 62% of the control. These results are interpreted as follows. Both Fractions P-5 and P-6 are heterogeneous; nevertheless, Fraction P-5, but not Fraction P-6, may be enriched with the plasma membrane, which is assumed to be associated with glucose transport activity. Fraction P-6 may be concentrated with the Golgi apparatus; however, the latter may not be the structure (or vesicles) to which (intracellular) glucose transport activity is associated. Insulin appears to increase the glucose transport activity in rat hearts, at least in part, by inducing translocation of the glucose transport mechanism from the unidentified vesicles (in Fraction P-6) to the plasma membrane (in Fraction P-5).
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PMID:Insulin action on glucose transport in cardiac muscle. 638 8

The glucose transport activity of fat cells was assayed in a cell-free system. The activity was solubilized and incorporated into egg-lecithin liposomes. The carrier-mediated glucose transport activity was estimated by subtracting the cytochalasin B-insensitive component from the total glucose uptake activity of the modified liposomes. When a crude microsomal preparation from fat cells was fractionated by sucrose density gradient centrifugation, two transport activities (peaks A and B) were separated. Peak A coincided with the peak of 5'-nucleotidase, a marker of the plasma membrane. Peak B appeared to coincide with the peak of UDPGal:N-acetylglucosamine galactosyltransferase, a marker of the Golgi apparatus. Peak A was considerably smaller than peak B under basal conditions. When cells were exposed to 1 nM insulin for 5 min before homogenization, the height of peak A increased whereas that of peak B decreased. Insulin had no significant effect on the galactosyltransferase activity. The Km values of glucose transport facilitated by the activities in peaks A and B were both approximately 10-15 mM. These results imply that insulin facilitates translocation of the transport activity from an intracellular storage site to the plasma membrane.
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PMID:Evidence that insulin causes translocation of glucose transport activity to the plasma membrane from an intracellular storage site. 677 56

Liver parenchymal cells from adult rats were isolated by treatment with collagenase and cultured as monolayers in Williams medium E with 10% fetal or calf serum. The additions of dexamethasone and insulin to the medium were essential for maintaining liver functions of the cells. These cells synthesized and secreted various serum proteins into the medium. Gluconeogenesis and glycogenolysis were enhanced by glucagon, and lipogenesis was stimulated by insulin. Many enzymes were also induced by various hormones. These activities were very low in freshly isolated cells, but were restored when the cells were cultured for a few days. Markers of plasma membranes, such as 5'-nucleotidase and insulin receptors, were reduced to half the normal levels on freshly isolated cells, but they were restored to the normal levels during culture of the cells without added hormones. Analysis of the profile of amino acids in the medium showed that freshly isolated cells were in a catabolic state of protein turnover and released branched chain amino acids into the medium, but that cultured cells consumed amino acids, not only for protein synthesis, but also for other metabolic processes, such as gluconeogenesis. These findings show that freshly isolated cells have impaired functions and are unsuitable for use in studies of liver metabolism, but that after culture for a few days the cells regain the activity of normal liver and hance become useful for studies of liver functions. Studies with these cells are simpler and give clear results than studies in vivo.
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PMID:Biochemical functions of adult rat hepatocytes in primary culture. 693 75

The glucose transport mechanism of rat epididymal fat cells was reconstituted into egg lecithin liposomes, and their carrier-mediated transport activity ws estimated from the difference in the rates of uptake of D-[3H]glucose and L-[14C]glucose. Insulin increased the glucose transport activity in the plasma membrane-rich fraction while decreasing the activity in the Golgi-rich fraction in agreement with our previous data (Suzuki, K., and Kono, T. (1980) Proc. Natl. Acad. Sci. U. S. A. 77, 2542-2545). The development of the insulin effects was inhibited when cells were exposed to 2,4-dinitrophenol or KCN before the insulin treatment. In addition, the reversal of the insulin effects was blocked upon exposure of insulin-treated cells to 2,4-dinitrophenol or KCN prior to the elimination of the hormone. In contrast, neither development nor reversal of the insulin effects was affected by cycloheximide or puromycin. The temperature coefficients of the transport activities reconstituted from the basal or insulin-treated forms of the plasma membrane-rich or Golgi-rich fractions were all identical. The recoveries of protein, 5'-nucleotidase, UDP-galactose:N-acetylglucosamine galactosyltransferase, and NADH dehydrogenase into subcellular fractions were determined. However, net effects of insulin on the glucose transport activities have remained unknown for lack of an appropriate marker enzyme of the Golgi-like vesicles associated with the transport activity. It is suggested that the glucose transport mechanism is recycled between the plasma membrane-rich and Golgi-rich fractions by an energy-dependent reaction.
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PMID:Energy-dependent and protein synthesis-independent recycling of the insulin-sensitive glucose transport mechanism in fat cells. 701 68

Plasma membrane was prepared from human placental tissue by two standard methods. The preparations, termed PVM and PPM, examined by electron microscopy and polyacrylamide gel electrophoresis, were characterized with respect to their binding properties for insulin, transferrin, alpha 2-macroglobulin and the immunoglobulins, IgM and IgG1. By means of sucrose density-gradient centrifugation, it was possible to fractionate the PVM into two distinct fractions. The first fraction, under the conditions used, was heavier (density greater than 1.080 g . cm-3) and was obtained as a pellet. It bound transferrin and IgM and had low specific activities for 5'-nucleotidase and for the binding of IgG1. The lighter fraction (density range 1.048-1.050 g . cm-3) had a high specific activity for 5'-nucleotidase and for IgG1 binding. Transferrin and IgM did not bind to this fraction. Insulin bound to both the fractions with comparable levels of specific binding activity, while alpha 2-macroglobulin binding was undetectable. The PPM preparation was found to have binding properties similar to those of the light fraction of PVM.
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PMID:Examination of different preparations of human placental plasma membrane for the binding of insulin, transferrin and immunoglobulins. 702 85

Hypertension is frequently associated with insulin-dependent diabetes mellitus, but the mechanism of the hypertension is unknown. An animal model of insulin-dependent diabetes mellitus hypertension could be helpful in determining the mechanism, but experimental insulin-dependent diabetes mellitus has been infrequently and irregularly associated with hypertension. In an attempt to develop a dependable model of insulin-dependent diabetes mellitus hypertension, we studied seven series of rats receiving either streptozotocin, surgical reduction of renal mass, or both. We found that superimposing streptozotocin 65 mg/kg body weight on 25% reduced renal mass regularly produced insulin-dependent diabetes mellitus and low-renin volume-expanded hypertension and that the animals remained healthy and hypertensive for as long as followed (13 weeks). Microalbuminuria correlated temporally with blood pressure. We used this dependable model to examine the role of endogenous digitalis-like substance in the development of hypertension in insulin-dependent diabetes mellitus. Plasma levels of digoxin-like immunoreactive factor (DIF), determined with a digoxin radioimmunoassay, were significantly higher in these hypertensive rats than in normotensive control rats (two-kidney diabetic rats, 25% reduced renal mass rats receiving vehicle for streptozotocin). This increase in plasma DIF was associated with a decrease in Na+, K(+)-ATPase activity in microsomes prepared from left or right ventricle. Microsomal 5'-nucleotidase, a plasma membrane marker, was unchanged. The plasma DIF level correlated inversely with myocardial Na+, K(+)-ATPase activity and positively with systolic blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Role of digitalis-like substance in experimental insulin-dependent diabetes mellitus hypertension. 750 18

Sulphonylurea drugs stimulate glucose transport and metabolism in muscle and fat cells in vitro. The molecular basis for the insulin-mimetic extrapancreatic effects of these oral antidiabetic therapeutic agents is unknown at present. Here we demonstrate that incubation of 3T3 adipocytes with the novel sulphonylurea, glimepiride, causes a time- and concentration-dependent release of the glycosylphosphatidylinositol (GPI)-anchored ecto-proteins, 5'-nucleotidase, lipoprotein lipase and a 62 kDa cyclic AMP (cAMP)-binding protein from the plasma membrane into the culture medium. The change in the localization is accompanied by conversion of the membrane-anchored amphiphilic proteins into their soluble hydrophilic versions, as judged by pulse-chase experiments and Triton X-114 partitioning, and by appearance of anti-cross-reacting determinant (CRD) immunoreactivity of the released proteins as shown by Western blotting. Metabolic labelling of cells with myo-[14C]inositol demonstrates that inositol is retained in the major portion of released lipoprotein lipase and cAMP-binding ectoprotein. The identification of inositol phosphate after deamination of these proteins with nitrous acid suggests cleavage of their GPI membrane anchor by a GPI-specific phospholipase C. However, after longer incubation with glimepiride the amount of soluble versions of the GPI-proteins lacking inositol and anti-CRD immunoreactivity increases, which may be caused by additional drug-stimulated hydrolytic events within their GPI structure or C-termini. Since insulin also stimulates membrane release of these GPI-modified proteins, and in combination with glimepiride in a synergistic manner, sulphonylurea drugs may exert their peripheral actions in adipose tissue by using (part of) the insulin postreceptor signalling cascade at the step of activation of a GPI-specific phospholipase C.
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PMID:The sulphonylurea drug, glimepiride, stimulates release of glycosylphosphatidylinositol-anchored plasma-membrane proteins from 3T3 adipocytes. 767 37

The impact of type 1 diabetes mellitus on liver gamma-glutamyltranspeptidase, a premalignant marker, was studied. Diabetes was induced in male Sprague Dawley and Fischer 344 rats by administration of Streptozotocin, which produced a stable and moderately severe diabetic state. In liver homogenates, gamma-glutamyltranspeptidase was increased over control levels: 1.2, 8.1 and 13.2 fold in Sprague-Dawley rats; 4.8, 58.4 and 84.7 fold in Fischer 344 rats; at 1, 3 and 6 weeks following Streptozotocin treatment. In plasma membranes isolated from the livers of Fischer 344 rats, gamma-glutamyltranspeptidase was increased over control levels: 5.6, 75 and 127 fold at weeks 1, 3 and 6 following Streptozotocin treatment. The relative specific activity of 5'-nucleotidase was found to be similar: 9-14, indicating comparable degrees of plasma membrane purity. Plasma glutamate-pyruvate transaminase levels were minimally and similarly affected at all time points indicating lack of association of increasing gamma-glutamyltranspeptidase activity with overt liver damage. Thyroid hormone replacement, with both T3 (0.6 micrograms/Kg) once a day and T4 (6.0 micrograms/kg) twice a day for three days elicited a further 30% increment in enzyme activity. Insulin replacement (20-40 units/200 g body weight) twice a day for five days reduced enzyme activity 51% at week 6. This was associated with an increase in gamma-glutamyltranspeptidase in the plasma from 14 fold over control levels in the diabetic state at week 6 to 53 fold over control levels after insulin replacement at week 6. It is proposed that the diabetes-induced increase in gamma-glutamyltranspeptidase is reduced by an insulin-directed shedding of the enzyme into the plasma.
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PMID:The impact of type I diabetes on rat liver gamma-glutamyltranspeptidase. 786 3

Primary hepatocytes were cultured on collagen gel in serum-free, alpha-modified Eagle's minimum essential medium containing 0.1 microM insulin, 0.1 microM dexamethasone, 10 mM pyruvate and supplements such as glucagon, epinephrine or growth hormone. The activities of alkaline phosphatase, 5'-nucleotidase and gamma-glutamyltransferase were assayed in cell extracts prepared from the cultures. All three enzyme activities were induced by glucagon, epinephrine or dibutyryl cAMP. The maximally effective concentration of glucagon was 5-10 nM for both alkaline phosphatase and 5'-nucleotidase and 100 nM for gamma-glutamyltransferase. Only alkaline phosphatase activity was suppressed by growth hormone, which caused marked suppression at about 1 microU (0.25 ng)/ml. Taurocholate also induced both alkaline phosphatase and gamma-glutamyltransferase activities at 1 mM.
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PMID:Hormonal regulations of alkaline phosphatase, 5'-nucleotidase and gamma-glutamyltransferase activities in adult rat hepatocytes cultured in serum-free medium on collagen gel. 809 10


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