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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous studies from our laboratory showed that diabetes increases platelet aggregation in rats, but only in washed platelets. In the present study, we evaluated platelet aggregation coupled with adenosine triphosphate (ATP) release in normal and diabetic rats using a whole blood electrical aggregometer. Additionally, we investigated the role of endothelium-derived relaxing factor, or nitric oxide, in the platelet reactivity in diabetic rats. Rats were made diabetic using streptozocin, 55 mg/kg. After 1 month the rats were anesthetized, and arterial blood samples were collected directly into sodium citrate solution 3.8%. Platelet counts and mean platelet volumes were determined. Platelet aggregation, disaggregation, and ATP release in response to adenosine diphosphate (ADP), collagen, and arachidonic acid were measured. Platelet aggregation in response to ADP, collagen, and arachidonic acid was not different in diabetic rats when compared with that in controls. However, ATP release in response to ADP was significantly increased in diabetic rats. Platelets from diabetic animals were significantly larger than those of controls. Nitro-L-arginine methyl ester, a nitric oxide synthase inhibitor, decreased platelet aggregation in response to ADP in the normal animals, but not in the diabetic animals. However, arginine-induced nitric oxide production decreased platelet aggregation and enhanced the occurrence of disaggregation in platelets from both normal and diabetic rats. From these studies, we conclude that platelet aggregation in diabetic rats is not different using whole blood electrical aggregation, but platelet ATP secretion is significantly enhanced. Additionally, nitric oxide may modulate the platelet aggregation, disaggregation, and ATP secretory response. However, it does not appear to be a major factor in the altered aggregation responses in diabetic rats.
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PMID:The effect of streptozocin-induced diabetes on platelet aggregation as determined by impedance aggregometry and platelet secretion: a possible role for nitric oxide. 766 98

This study was undertaken to compare the ability of two guanidine compounds (aminoguanidine and methylguanidine), with different in vitro effects on NO synthase activity and AGE formation, to inhibit diabetic vascular dysfunction developing early after the onset of diabetes. In rats with STZ-induced diabetes of 5-wk duration, regional vascular [125I]albumin permeation was increased about two- to threefold in ocular tissues, sciatic nerve, and aorta; in general, both guanidine compounds normalized albumin permeation in diabetic rats without affecting it in controls. Methylguanidine was only approximately 7% as effective as aminoguanidine as an inhibitor of AGE formation from L-lysine and G6P; both compounds were poor inhibitors of AR. Methylguanidine was approximately 1-5% as potent as aminoguanidine and L-NMMA as an inhibitor of the cytokine- and endotoxin-inducible isoform of NO synthase. In contrast, the potency of methylguanidine as an inhibitor of the constitutive isoform of NO synthase was comparable to that of aminoguanidine, and both guanidine compounds were much less effective than L-NMMA. These observations suggest a role for a relative or absolute increase in NO production in the pathogenesis of early diabetic vascular dysfunction and raise the possibility that inhibition of diabetic vascular functional changes by aminoguanidine may reflect inhibition of NO synthase activity rather than, or in addition to, prevention of AGE formation.
Diabetes 1993 Feb
PMID:Prevention of diabetic vascular dysfunction by guanidines. Inhibition of nitric oxide synthase versus advanced glycation end-product formation. 767 25

Overproduction of the free radical nitric oxide (NO) has been implicated in the pathogenesis of a variety of inflammatory and immunologically mediated diseases as well as complications of diabetes. In the present study we have demonstrated that aminoguanidine selectively inhibits the cytokine-inducible isoform of NO synthase which appears to be responsible for the excess production of NO linked to these disease states. By using organ, cell, and enzyme-based measurements we have shown that aminoguanidine is equipotent to NG-monomethyl-L-arginine (L-NMA) as an inhibitor of the cytokine-induced isoform of NO synthase but is 10 to 100-fold less potent as an inhibitor of the constitutive isoform. Thus, aminoguanidine may be useful as a selective inhibitor of the inducible NO synthase in the treatment of disease states characterized by the pathological overproduction of NO.
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PMID:Selective inhibition of the inducible nitric oxide synthase by aminoguanidine. 768 10

The inducible NO synthase (iNOS) was found to be expressed in pancreatic lesions of adult diabetes-prone BB rats. Pancreatic iNOS mRNA was detected by reverse transcriptase PCR in pancreatic RNA of adult diabetes-prone BB rats but not in normal Wistar rats, young diabetes-prone BB rats without insulitis or in diabetes-resistant BB rats. Immunohistochemistry of pancreatic sections using an iNOS-specific antiserum labeled the pancreas of adult diabetes-prone BB rats but not Wistar rats. Parallel staining for ED1-positive macrophages showed restriction of iNOS expression to areas of islet infiltration by macrophages. In conclusion, the data provide direct evidence for enhanced expression of inducible NO synthase in tissue lesions during the development of autoimmune diabetes.
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PMID:Transcription and translation of inducible nitric oxide synthase in the pancreas of prediabetic BB rats. 768 27

Nitric oxide (NO) generation may be a final common pathway for beta-cell damage in early insulin-dependent diabetes mellitus. Insulin-producing cells express an inducible form of NO synthase (iNOS), which is similar to that observed in activated macrophages. Induction of iNOS mRNA in these cells depends on protein synthesis. To further characterize the regulation of iNOS induction in insulin-producing cells, RINm5F cells (RIN cells) were exposed for 6 h to human recombinant interleukin-1 beta (rIL-1 beta; 1 ng/ml) alone or in combination with either nicotinamide (10, 20, or 50 mM) or dexamethasone (1 or 5 microM). These agents have been previously shown to prevent activation of iNOS in macrophages, fibroblasts, and hepatocytes. rIL-1 beta induced the expression of iNOS mRNA in RIN cells and a 12- to 13-fold increase in medium nitrite accumulation, the latter indicating NO production. Nicotinamide decreased nitrite production in a dose-dependent way. Thus, 10 mM nicotinamide decreased rIL-1 beta-induced nitrite formation by 30%, 20 mM by 60%, and 50 mM by 90%. The highest concentration of nicotinamide also prevented rIL-1 beta-induced iNOS mRNA, an effect associated with inhibition of total protein biosynthesis. However, 10 or 20 mM nicotinamide did not modify rIL-1 beta-induced iNOS mRNA expression or inhibit protein biosynthesis. Dexamethasone also decreased rIL-1 beta-induced nitrite production without affecting iNOS mRNA expression. As a whole, these data suggest that both nicotinamide and dexamethasone may prevent NO accumulation in insulin-producing cells by posttranscriptional mechanisms. It is also possible that these drugs induce direct inhibition of iNOS enzymatic activity and/or scavenge NO. Higher concentrations of nicotinamide might also inhibit iNOS mRNA expression, possibly by blocking protein biosynthesis.
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PMID:Nicotinamide and dexamethasone inhibit interleukin-1-induced nitric oxide production by RINm5F cells without decreasing messenger ribonucleic acid expression for nitric oxide synthase. 769 79

The effect of inhibiting nitric oxide synthase (N omega-nitro-L-arginine) on plasma extravasation induced by intravenously administered substance P, [pGlu5,Me-Phe8,Sar9]substance P-(5-11) or prostaglandin E2 was examined. Control rats were more responsive than diabetic rats to both substance P and [pGlu5,Me-Phe8,Sar9]-substance P-(5-11). N omega-Nitro-L-arginine blocked the actions of substance P on dorsal skin, but potentiated those of [pGlu5,Me-Phe8,Sar9]substance P-(5-11) in control rats. In diabetic rats N omega-nitro-L-arginine, which did not affect the actions of the substance P analogue, exerted complex effects on substance P induced plasma extravasation giving potentiation in the tongue, inhibition in bronchioles, and no effect in other tissues. N omega-Nitro-L-arginine inhibited prostaglandin E2 induced extravasation in control, but not diabetic rats. The altered plasma extravasation in diabetic rats may be due to diabetes induced alterations in nitric oxide synthesis or in the responses of the endothelial cells to nitric oxide.
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PMID:Altered vascular permeability responses to substance P in diabetic rats: interactions with a nitric oxide synthesis inhibitor. 769 56

Experiments were performed to determine the influence of endogenous nitric oxide (NO) on basal arteriolar diameter in kidneys from diabetic rats and to evaluate the role of superoxide anions as modulators of NO activity under these conditions. Male Sprague-Dawley rats were injected with streptozotocin (STZ, 65 mg/kg i.v.) and received insulin via ip osmotic minipumps (3 U/kg per day). Sham rats received vehicle treatments. Videomicroscopy was used, in conjunction with the in vitro blood-perfused juxtamedullary nephron technique, to visualize renal afferent and efferent arterioles 2 wk after the onset of diabetes. Baseline afferent arteriolar inside diameter was greater in STZ (32 +/- 2 microns) than in sham rats (24 +/- 2 microns). Efferent arteriolar diameter did not differ between STZ (24 +/- 2 microns) and sham rats (21 +/- 1 microns). In kidneys from sham rats, N omega-nitro-L-arginine (L-NNA, an NO synthase inhibitor) decreased arteriolar diameters in a concentration-dependent manner, with 100 microM L-NNA significantly reducing both afferent (13 +/- 2%) and efferent (11 +/- 1%) diameters. In kidneys from STZ rats, 100 microM L-NNA reduced afferent and efferent diameters by only 3 +/- 1 and 4 +/- 1%, respectively, indicating a suppressed arteriolar influence of NO. In STZ kidneys treated with superoxide dismutase (SOD, 150 U/mL), afferent and efferent arteriolar L-NNA responses were restored to levels comparable to those of SOD-treated and untreated sham kidneys. These observations suggest that suppressed SOD activity reduces the tonic influence of NO on renal arterioles during the early stage of diabetes mellitus, perhaps through allowing the accumulation of NO-scavenging superoxide anions.
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PMID:Superoxide dismutase restores the influence of nitric oxide on renal arterioles in diabetes mellitus. 775 88

Defective endothelium-dependent relaxation in diabetic blood vessels may be regulated at the site of synthesis. We tested the hypothesis that acute administration of L-arginine (L-Arg) as substrate for endothelium-derived relaxing factor (EDRF) would normalize defective relaxation to acetylcholine (ACh) in streptozotocin-induced diabetic rat aortic rings. Plasma concentrations of basic amino acids (e.g., arginine, lysine, and histidine) were significantly reduced by diabetes, but variable results (increased, decreased, or no change) were observed in plasma concentrations of neutral amino acids. Endothelium-dependent relaxation to ACh (but not calcium ionophore A23187) was impaired in diabetic rings. Relaxation to nitroglycerin (NTG) was not altered. Pretreatment with L-nitroarginine methyl ester (L-NAME), a nitric oxide (NO) synthase inhibitor, blocked the relaxation to ACh and A23187 but not relaxation to NTG in both control and diabetic rings. Pretreatment with 3 mM L-Arg (but not D-Arg) potentiated the relaxation to ACh in diabetic rings. L-Arg had no effect on ACh-induced relaxation in control rings or on relaxation to NTG in control or diabetic rings. A mechanism for impaired endothelium-dependent relaxation to ACh in diabetic aorta may arise from a defect in utilization of L-Arg by NO synthase for production of EDRF/NO.
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PMID:Amelioration by L-arginine of a dysfunctional arginine/nitric oxide pathway in diabetic endothelium. 776 4

Splenic cells from the diabetes-prone BB rat show reduced proliferative responses to concanavalin A (ConA) and other mitogens. This study was undertaken to test whether this reduced lymphoproliferation in the BB rat is mediated by an increased production of nitric oxide (NO) by macrophages. Splenic leukocytes from diabetes-prone BB rats and five strains of control rats (BB-R, Wistar-Furth, Sprague-Dawley, Wistar, and Lewis) were cultured in RPMI-1640 media containing ConA. The leukocytes from BB rats showed reduced [3H]thymidine uptake and increased release of NO compared with the control rats. Partial depletion of macrophages from the culture or incubation with -NG-monomethylarginine (NGMMA), a specific NO synthase inhibitor, markedly augmented ConA-induced proliferation of the splenic leukocytes from BB but not the control rats. Enrichment of BB rat macrophages suppressed the proliferation of BB-R rat spleen cells. Excess L-arginine added to the culture reversed the NGMMA effect. These results suggest that increased production of NO by macrophages is partly responsible for the reduced proliferative responses of splenic leukocytes in the BB rat.
Diabetes 1994 Oct
PMID:Nitric oxide produced by macrophages mediates suppression of ConA-induced proliferative responses of splenic leukocytes in the diabetes-prone BB rat. 792 91

Cytokines may be important mediators of beta-cell damage in early insulin-dependent diabetes mellitus. In order to further characterize the mechanism(s) of action of cytokines on insulin-producing cells, mouse pancreatic islets were exposed for 48 h to IL-1 beta, IFN-gamma or TNF-alpha, alone or in combinations. The three cytokines induced islet nitric oxide (NO) production, an effect most marked when islets were exposed to the three cytokines together. In parallel with NO production, IL-1 beta+IFN-gamma+TNF-alpha impaired islet function, as judged by decreased islet DNA and insulin content, decreased glucose metabolism and decreased glucose-induced insulin release. Aminoguanidine, an inhibitor of NO production, prevented all the above described suppressive effects of the cytokines, with exception of depletion in islet insulin content. In parallel experiments, insulin-producing RIN cells were exposed for 6 h to the same cytokines. Both IL-1 beta and TNF-alpha, but not IFN-gamma, induced NO production and expression of the mRNA encoding for the inducible form of the enzyme NO synthase (iNOS). These effects were most pronounced when combinations of IL-1 beta+IFN-gamma or IL-1 beta+IFN-gamma+TNF-alpha were used. As a whole, the data suggest that combinations of cytokines induce higher amounts of NO generation by mouse pancreatic islets than each of the cytokines isolated. An important source of islet NO production are probably the beta-cells, as pointed by data obtained with an insulinoma cell line. Most of the deleterious effects of the cytokines of mouse islets are prevented by blocking NO production, suggesting that NO is the main mediator of cytokine-induced beta-cell damage.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:TNF-alpha and IFN-gamma potentiate the deleterious effects of IL-1 beta on mouse pancreatic islets mainly via generation of nitric oxide. 794 48


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