Glomerular hemodynamic alterations during acute hyperinsulinemia in normal and diabetic rats.

Treatment of insulin dependent diabetes invariably requires exogenous insulin to control blood glucose. Insulin treatment, independent of other factors associated with insulin dependent diabetes, may induce changes that affect glomerular function. Due to exogenous delivery of insulin in insulin dependent diabetes entering systemic circulation prior to the portal vein, plasma levels of insulin are often in excess of that observed in non-diabetics. The specific effects of hyperinsulinemia on glomerular hemodynamics have not been previously examined. Micropuncture studies were performed in control (non-diabetic), untreated diabetic and insulin-treated diabetic rats 7 to 10 days after administration of 65 mg/kg body weight streptozotocin. After the first period micropuncture measurements were obtained, 5 U of regular insulin (Humulin-R) was infused i.v., and glucose clamped at euglycemic values (80 to 120 mg/dl). Blood glucose concentration in non-diabetic controls was 99 +/- 6 mg/dl. In control rats, insulin infusion and glucose clamp increased nephron filtration rate due to decreases in both afferent and efferent arteriolar resistance (afferent greater than efferent) resulting in increased plasma flow and increased glomerular hydrostatic pressure gradient. However, insulin infusion and glucose clamp produced the opposite effect in both untreated and insulin-treated diabetic rats with afferent arteriolar vasoconstriction resulting in decreases in plasma flow, glomerular hydrostatic pressure gradient and nephron filtration rate. Thromboxane A2 (TX) synthetase inhibition partially decreased the vasoconstrictive response due to acute insulin infusion in diabetic rats preventing the decrease in nephron filtration rate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Amylin and bone metabolism in streptozotocin-induced diabetic rats.

Amylin (AMY) is a 37 amino acid peptide cosecreted with insulin (INS) by pancreatic beta-cells and absent in type 1 diabetes, a condition frequently associated with osteopenia. AMY binds to calcitonin receptors, lowers plasma calcium concentration, inhibits osteoclast activity, and stimulates osteoblasts. In the present study, we examined the effects of AMY replacement on bone loss in a streptozotocin (STZ)-induced rodent model type 1 diabetes. Of 50 male Wistar rats studied, 40 were made diabetic with intraperitoneal STZ (50 mg/kg; plasma glucose concentrations > 11 mM within 5 days). Ten nondiabetic control (CONT) rats received citrate buffer without STZ. Diabetic rats were divided into four groups (n = 10/group) and injected subcutaneously with rat AMY (45 mg/kg), INS (12 U/kg), both (same doses), or saline (STZ; diabetic controls) once per day. After 40 days of treatment and five 24-h periods of urine collection for deoxypyridinoline (DPD), the animals were killed, blood was sampled, and femurs were removed. The left femur was tested for mechanical resistance (three-point bending). The right femur was tested for total, diaphyseal (cortical bone), and metaphyseal (trabecular bone) bone densities using dual-energy X-ray absorptiometry (DXA). Bone was ashed to determine total bone mineral (calcium) content. None of the treatments had any significant effect on femoral length and diameter. Untreated diabetic rats (STZ; 145+/-7N) had lower bone strength than did nondiabetic CONT (164+/-38; p < 0.05). Total bone mineral density (BMD; g/cm2) was significantly lower in STZ (0. 2523+/-0.0076) than in CONT (0.2826+/-0.0055), as were metaphyseal and diaphyseal densities. Diabetic rats treated with AMY, INS, or both had bone strengths and bone densities that were indistinguishable from those in nondiabetic CONT. Changes in bone mineral content paralleled those for total BMD (T-BMD). Plasma osteocalcin (OC) concentration, a marker for osteoblastic activity, was markedly lower in untreated diabetic rats (7. 6+/-0.9 ng/ml); p < 0.05) than in nondiabetic CONT (29.8+/-1.7; p < 0.05) or than in AMY (20.1+/-0.7; p < 0.05). Urinary DPD excretion, a marker for bone resorption, was similar in untreated and AMY-treated diabetic rats (35.0+/-3.1 vs. 35.1+/-4.4 nmol/mmol creatinine), intermediate in rats treated with INS (49.9+/-2.7), and normalized in diabetic rats treated with both agents (58.8+/-8.9 vs. 63.2+/-4.5 in CONT). Thus, in our STZ rat model of diabetic osteopenia, addition of AMY improved bone indices apparently by both inhibiting resorption and stimulating bone formation.     

Glomerular size-selectivity and microalbuminuria in early diabetic glomerular disease.

Sieving coefficients of uncharged dextrans of graded size (radii 30 to 60 A) were used to characterize barrier size-selectivity in nonazotemic diabetic humans with microalbuminuria (Group 1, N = 11) or macroalbuminuria (Group 2, N = 21). Compared to a non-diabetic control group (N = 21) the low radius end of the sieving profile was depressed, whereas the high radius end was elevated in each diabetic group, more so in Group 2 than Group 1. A heteroporous membrane model revealed the major portion of the glomerular barrier to be perforated by restrictive pores of approximately 56 A radius in all three groups. However, in keeping with a parallel trend for GFR, the relative density of restrictive pores was control greater than Group 1 greater than Group 2. The remaining minor portion of the barrier was perforated by large, shunt-like pores, the relative prominence of which ranked Group 2 greater than Group 1 greater than control. Although the hypothetical, fractional clearance of macromolecules attributable to the shunt-like pores varied directly with fractional clearances of albumin and IgG, the progressive increment in the latter fractional protein clearances in the two diabetic groups was disproportionate. This raises the possibility that factors in addition to barrier size defects contribute to the development, magnitude and composition of proteinuria early in the course of diabetic glomerular disease.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma glucose-lowering effect of tramadol in streptozotocin-induced diabetic rats.

The effect of tramadol on the plasma glucose level of streptozotocin (STZ)-induced diabetic rats was investigated. A dose-dependent lowering of plasma glucose was seen in the fasting STZ-induced diabetic rats 30 min after intravenous injection of tramadol. This effect of tramadol was abolished by pretreatment with naloxone or naloxonazine at doses sufficient to block opioid mu-receptors. However, response to tramadol was not changed in STZ-induced diabetic rats receiving p-chlorophenylalanine at a dose sufficient to deplete endogenous 5-hydroxytrptamine (5-HT). Therefore, mediation of 5-HT in this action of tramadol is ruled out. In isolated soleus muscle, tramadol enhanced the uptake of radioactive glucose in a concentration-dependent manner. The stimulatory effects of tramadol on glycogen synthesis were also seen in hepatocytes isolated from STZ-induced diabetic rats. The blockade of these actions by naloxone and naloxonazine indicated the mediation of opioid mu-receptors. The mRNA and protein levels of the subtype 4 form of glucose transporter in soleus muscle were increased after repeated treatments for 4 days with tramadol in STZ-induced diabetic rats. Moreover, similar repeated treatments with tramadol reversed the elevated mRNA and protein levels of phosphoenolpyruvate carboxykinase in the liver of STZ-induced diabetic rats. These results suggest that activation of opioid mu-receptors by tramadol can increase the utilization of glucose and/or decrease hepatic gluconeogenesis to lower plasma glucose in diabetic rats lacking insulin.     

Glycosylated hemoglobins: increased glycosylation of hemoglobin A in diabetic patients.

The components of the hemoglobin-A1 fraction--hemoglobins A1a--c--arise from nonenzymatic glycosylation of hemoglobin A at the beta-chain N-terminal amino groups and can be resolved from hemoglobin A by cation exchange chromatography. Glycosylation can also occur at the alpha-chain N-terminals as well as the epsilon-amino groups of lysine residues of both alpha- and beta-chains; this results in glycosylated species appearing in the hemoglobin-A fraction. In this study, we determined the extent of hemoglobin-A glycosylation using a colorimetric chemical method specific for the detection of ketoamine-linked hexoses in proteins. We demonstrate increased glycosylation of the main hemoglobin-A fraction in diabetic patients, which correlates significantly (r = 0.72, P less than 0.001) with the hemoglobin-A1 percentage determined by column chromatography in the corresponding hemolysates. This finding provides the basis for the application of this chemical procedure to the measurement of total glycosylation of hemoglobin.     

晚期糖基化终末产物和蛋白激酶C对糖尿病大鼠肾脏的影响

目的探讨糖尿病状态下肾小球晚期糖基化终末产物（ＡＧＥ）与蛋白激酶Ｃ（ＰＫＣ）的关系及其对肾脏的影响。方法给予糖尿病大鼠胰岛素和氨基胍治疗，测定血糖，糖化血红蛋白Ａ１Ｃ（ＨｂＡ１Ｃ）、肾小球ＡＧＥ（ＧＴＥＡＧＥ）、蛋白激酶Ｃ（ＰＫＣ）、肾小球基底膜厚度（ＧＢＭＴ）和尿Ｐｒ／Ｃｒ比值。结果糖尿病大鼠在血糖、ＨｂＡ１Ｃ和ＡＧＥ水平增高的同时，ＰＫＣ活性、尿Ｐｒ／Ｃｒ比值和ＧＢＭＴ都显著增加（Ｐ值小于００１）；胰岛素可减少ＨｂＡ１Ｃ和ＡＧＥ形成，恢复ＰＫＣ活性，氨基胍可减少ＡＧＥ形成，但对ＰＫＣ活性无影响。两种药物均可减缓尿Ｐｒ／Ｃｒ比值和ＧＢＭＴ增加（Ｐ＜００１或Ｐ＜００５）。结论慢性高血糖可增高肾小球ＰＫＣ活性，非酶促糖基化可能未直接参与ＰＫＣ活性改变，但ＰＫＣ可加强ＡＧＥ对肾脏的影响。减少ＡＧＥ形成，改善ＰＫＣ活性对糖尿病肾病的防治尤为重要。     

Kallikrein gene delivery improves serum glucose and lipid profiles and cardiac function in streptozotocin-induced diabetic rats

We investigated the role of the kallikrein-kinin system in cardiac function and glucose utilization in the streptozotocin (STZ)-induced diabetic rat model using a gene transfer approach. Adenovirus harboring the human tissue kallikrein gene was administered to rats by intravenous injection at 1 week after STZ treatment. Human kallikrein transgene expression was detected in the serum and urine of STZ-induced diabetic rats after gene transfer. Kallikrein gene delivery significantly reduced blood glucose levels and cardiac glycogen accumulation in STZ-induced diabetic rats. Kallikrein gene transfer also significantly attenuated elevated plasma triglyceride and cholesterol levels, food and water intake, and loss of body weight gain, epididymal fat pad, and gastrocnemius muscle weight in STZ-induced diabetic rats. However, these effects were blocked by icatibant, a kinin B2 receptor antagonist. Cardiac function was significantly improved after kallikrein gene transfer as evidenced by increased cardiac output and +/-delta P/delta t (maximum speed of contraction/relaxation), along with elevated cardiac sarco(endo)plasmic reticulum (Ca2+ + Mg2+)-ATPase (SERCA)-2a, phosphorylated phospholamban, NOx and cAMP levels, and GLUT4 translocation into plasma membranes of cardiac and skeletal muscle. Kallikrein gene delivery also increased Akt and glycogen synthase kinase (GSK)-3beta phosphorylation, resulting in decreased GSK-3beta activity in the heart. These results indicate that kallikrein through kinin formation protects against diabetic cardiomyopathy by improving cardiac function and promoting glucose utilization and lipid metabolism.     

Structural alterations to the podocyte are related to proteinuria in type 2 diabetic patients.

BACKGROUND: The podocyte is believed to play a key role in maintaining the integrity of the glomerular filtration barrier, and damage or loss has been linked to the development of albuminuria. METHODS: Renal biopsies from 16 type 2 diabetic patients with nephropathy and 28 non-diabetic controls were analysed using light and electron microscopy. RESULTS: Podocyte number per glomerulus was significantly lower in the type 2 patients compared with controls [mean (95% confidence interval) 464 (382-546) vs 589 (543-635), P = 0.004]. Mean glomerular volume was significantly increased in diabetic patients compared with controls [5.5 (4.9-6.1) vs 3.1 (2.7-3.5) x 10(6) microm(3), P<0.001], thus the diabetic patients demonstrated an even greater proportional reduction in podocyte density per glomerulus [88 (68-108) vs 201 (182-220)/10(6) microm(3), P<0.001]. Podocyte foot process width on both the filtration surface (FPWgbm) and mesangial surface (FPWmes) was significantly increased compared with controls [796 (708-884) vs 556 (460-908) nm, P = 0.001; 1108 (821-1394) vs 760 (555-1078) nm, P = 0.029, respectively]. There was a significant negative correlation between proteinuria and both podocyte number and podocyte density per glomerulus (r = -0.63, P = 0.009; r = -0.58, P = 0.018, respectively). There was a significant positive correlation between proteinuria and both FPWgbm and FPWmes (r = 0.64, P = 0.008, for both). CONCLUSION: Podocyte loss occurs in type 2 diabetic nephropathy and is related to increasing proteinuria. Whether the accompanying glomerular enlargement and widening of foot processes are a cause of podocyte loss is uncertain. Longitudinal studies are required to determine the sequence of events leading to podocyte loss in diabetic nephropathy.     

Demonstration of altered antithrombin III activity due to nonenzymatic glycosylation at glucose concentration expected to be encountered in severely diabetic patients

The effect of nonenzymatic glycosylation on the kinetics and structure-function relationships of antithrombin III were investigated at normal physiologic concentrations of antithrombin III and glucose, which are 5.2 microM and 5 mM, respectively. The results were compared with antithrombin III incubated at the glucose concentration expected to be found in severely diabetic patients (15 mM). Antithrombin III incubated at 5 mM lost 33% of the heparin cofactor activity after 7 days, whereas antithrombin III incubated at 15 mM lost 50% for the same period. Under both conditions, half of the heparin cofactor activity was lost after 15 days. When D-[U-14C]glucose was used as tracer, approximately 0.6 mol glucose/mol protein was incorporated after 10 days at both concentrations of glucose. A detailed evaluation of the kinetics of inhibition of thrombin by glycosylated antithrombin III revealed that the second-order rate constant is three times smaller than that of normal antithrombin III. On the basis of these data, it is concluded that glycosylated antithrombin III with 50% depressed heparin cofactor activity is three times weaker than normal antithrombin III as an inhibitor of thrombin. The implications of these observations with respect to the possible pathogenesis of thrombosis in diabetes are discussed.     

Allotransplantation of rat islets into the cisterna magna of streptozotocin-induced diabetic rats.

Islets were isolated from the pancreata of Sprague-Dawley rats and transplanted into streptozotocin-induced diabetic outbred Wistar rats. The effect of transplantation of islets into the cisterna magna on the diabetic state of the recipients was compared with that of the conventional transplantation of islets into liver via the portal vein. After successful intraportal (IP) transplantation, rejection took place between days 7 and 15 in all diabetic recipients. All of the eleven rats surviving after stereotaxic implantation of islets into the cisterna magna returned to normoglycemia within 7 days after transplantation. Nine of the recipients with intra-cisterna magna (IM) islet allografts were still normoglycemic at 210 days after transplantation. The glucose disappearance rate of the IM transplant rats was slower than that of the IP transplant rats, and blood glucose returned to the normal basal level within 5 hr following glucose administration. Although the insulin levels were almost undetectable in cerebrospinal fluid before IM transplantation, the insulin levels were markedly increased after IM transplantation and twice as great in CSF than blood. Thus, these findings indicate that the cisterna magna can serve as an immunologically privileged site for implantation of allogeneic pancreatic islets, and islets in CSF can regulate and maintain normal glucose homeostasis via secretion of insulin across the blood-brain barrier.     

Glycosaminoglycans prevent morphological renal alterations and albuminuria in diabetic rats.

Abnormal glycosaminoglycan metabolism is involved in the onset of anatomo-functional derangements in diabetic nephropathy, and determines the loss of glomerular basement membrane anionic charges leading to albuminuria. Glycosaminoglycan administration was shown to increase the negative electrical potential of the vessel wall, inhibit mesangial cell proliferation, which is an anatomical hallmark of diabetic nephropathy, and slow down the progression to uremia in subtotally nephrectomized rats, a model that shares some pathogenetic key events with diabetic nephropathy. Based on these considerations, we verified the effect of exogenous glycosaminoglycans on renal involvement in streptozotocin diabetic rats. Long-term administration of two glycosaminoglycans (low-molecular weight heparin and dermatan sulphate) prevented glomerular basement membrane thickening, glomerular anionic charge reduction, as well as the onset of albuminuria without affecting glomerular filtration rate and metabolic control of the disease. Our data demonstrate that the long-term administration of glycosaminoglycans has a favorable effect on morphological and functional renal abnormalities in diabetic rats.     

Heterozygous mice for TGF-betaIIR gene are resistant to the progression of streptozotocin-induced diabetic nephropathy

BACKGROUND: Transforming growth factor-beta (TGF-beta) receptor complex and its downstream Smad signaling intermediates constitute an extracellular matrix (ECM) accumulation pathway. METHODS: In the present study, we examined whether decreased expression of the TGF-beta type II receptor (TGF-betaIIR) in TGF-betaIIR gene heterozygous (TGF-betaIIR+/-) (HT) mice could inhibit the Smad signaling pathway and subsequent progression of renal lesions when streptozotocin (STZ) diabetes is induced. RESULTS: At the end of the 28-week experiment after STZ injections, wild-type diabetic mice showed severe glomerular hypertrophy and mesangial matrix accumulation occasionally featuring nodular glomerulosclerosis. In contrast, mean glomerular area and mesangial volume density were significantly decreased in the HT diabetic mice as compared with the wild-type diabetic mice. Immunostaining for phosphorylated Smad2/Smad3 and TGF-betaIIR in the glomerular cells was also significantly reduced in the HT diabetic mice. Southwestern histochemistry using digoxigenin-labeled CAGA sequence probes showed that localization of labeled probes to the nuclei of glomerular cells in the HT diabetic mice was significantly less frequent than that in the wild-type diabetic animals. Northern blot analysis showed that alpha1(IV) collagen mRNA levels were significantly reduced in the kidney tissue of HT diabetic mice as compared with the wild-type diabetic mice. CONCLUSION: These results suggest that decreased expression of TGF-betaIIR in the HT diabetic mice can inhibit the progression of diabetic renal injury by inhibiting the downstream Smad signaling pathway and subsequent ECM gene expression. Thus, TGF-betaIIR appears to play an important role in the progression of diabetic nephropathy by mediating intracellular Smad signaling.     

Inhibition of cyclooxygenase-2 expression contributes to podocyte injury in streptozotocin-induced diabetic rats

Objective To investigate the role of cyclooxygenase-2 (COX-2) in podocyte injury in diabetic rats mediated by the disruption of low-density lipoprotein receptor (LDLr) pathway. Methods Eight-week old male Sprague-Dawley (SD) rats were treated for 12 weeks by dividing into three groups: control rats, streptozotocin (STZ) induced diabetic rats (DM), and diabetic rats treated with aspirin (DM+Aspirin). The plasma lipid profile was checked by clinical biochemistry assay. The ratio of urinary microalbumin to creatinine (ACR) was detected by enzyme-linked immunosorbent assay. Intracellular lipid accumulation was evaluated by Oil Red O staining and a free cholesterol quantitative assay. The glomerular podocyte injury and the expression of molecules related with LDLr pathway were evaluated by electron microscope, immunohistochemical staining, immunofluorescent staining, and Western blotting. Results There were increased levels of urinary ACR (P＜0.01) and podocyte injury(P＜0.01) in DM rats compared with the controls. Additionally, lipid accumulation in kidneys of DM rats were significantly increased (P＜0.01), due to increased protein expressions of COX-2, LDLr, sterol regulatory element–binding protein (SREBP) cleavage activating protein (SCAP), and SREBP-2 (P＜0.01). However, these changes were significantly inhibited by an inhibitor of COX-2, Aspirin (P＜0.05). It's worth noting that, COX-2 protein expression was closely correlated with LDLr protein expression (r=0.85, P＜0.01). Conclusion Dysregulation of LDLr pathway contributes to podocyte injury in diabetic nephropathy, which may be mediated through the increased COX-2 expression.     

Ultra-structural morphological abnormalities of the urinary bladder in streptozotocin-induced diabetic female rats

The objective of this study was to evaluate the ultra-structural changes in the urinary bladder of diabetic rats in relation to disease duration since the morphological bases of diabetes-induced bladder dysfunction are poorly understood. Urinary bladders were examined chronologically by electron microscopy in a female Wistar-rat model of streptozotocin-induced diabetes mellitus and compared to control samples. Numerous dark mitochondria with swollen cristae and electron lucent, large, calcified and degenerated mitochondria were observed first in the urothelium. Intraepithelial capillaries surrounded by thick collagen were also present. Gap junctions between myocytes were interrupted or extensively widened with reduced mitochondria and caveolae. Collagen accumulation, degenerated nerve fibres and myelin bodies were seen between myocytes with increased collagen content and frequent mast cells, phagocytes and lymphocyte aggregates in the stroma. All ultra-structural lesions became augmented with longer duration of diabetes. Diabetes induces time-dependent pathologic changes in the urinary bladder of rats that might account for bladder dysfunction.     

Glomerular structure and function in diabetic nephropathy. Early to advanced stages

Kidney biopsies from 14 insulin-dependent diabetes mellitus patients with persistent albuminuria were studied by light and electron microscopy. In terms of kidney function, the patients spanned stages from early to advanced nephropathy. The clinical parameters were (ranges, with medians in parentheses) urinary albumin excretion (UAE) 158-5494 micrograms/min (1153 micrograms/min), glomerular filtration rate (GFR) 30-128 ml.min-1 x 1.73 m-2 (90 ml.min-1 x 1.73 m-2) and mean arterial blood pressure (BP) 87-122 mmHg (109 mmHg). The severity of clinical nephropathy (UAE, GFR, and BP together) correlated with an index of the structural lesions (basement membrane [BM] thickness, mesangial expansion, and glomerular occlusion together; r = 0.62, 2P less than 0.05). GFR compared with remnant surface of glomerular capillaries (filtration surface; FS) gave values of r = 0.72 and 2P = 0.004, and UAE compared with the percentage of the peripheral BM surface carrying fluffy loose intrinsic fine structure gave r = 0.62 and 2P = 0.02. BP per se did not correlate with structural parameters. The area of FS per open glomerulus did not decrease with increasing mesangial volume fraction, which indicates compensatory changes of the capillaries in early and advanced stages of glomerulopathy. In 7 patients with less than 10% occluded glomeruli, correlations between glomerular volume and the parameters of diabetic glomerulopathy (i.e., BM thickness and volume fractions of mesangium and mesangial matrix) failed to reach statistical significance. The actual glomerular volume, however, is a product of the individual's original glomerular volume, probably the early diabetic hypertrophy and modifying changes consequent to the development of glomerulopathy.(ABSTRACT TRUNCATED AT 250 WORDS)     

L-lysine reduces nonenzymatic glycation of glomerular basement membrane collagen and albuminuria in diabetic rats

In this study, we examined the hypothesis whether exogenous administration of L-lysine in drinking water would reduce nonenzymatic glycation of glomerular basement membrane (GBM) collagen and thus albuminuria in streptozotocin-diabetic rats. The rationale is that the administered lysine would combine with the circulating glucose and make it unavailable to react with epsilon-amino groups of lysine of various proteins in these diabetic rats. Lysine (0.1%) was given to diabetic rats 7 days (early treatment) or 90 days (late treatment) after induction of hyperglycemia. The treatment was continued for 60 days. Diabetic rats had significantly higher glucose, glycosylated HbA(1), kidney weight, nonenzymatic glycation of GBM collagen, albuminuria, and systolic blood pressure than normal rats. Early treatment with lysine prevented the rise in glycosylated HbA(1) (normal 6.98 +/- 0.71% vs. diabetic - early treatment - 7.78 +/- 1.50%; p = NS), reduced glycosylation of GBM collagen by 86%, and significantly improved albuminuria. There was no significant effect on plasma glucose and systolic blood pressure. However, late treatment reduced the glycosylation of GBM collagen by 46% with a significant improvement in albuminuria. Plasma creatinine levels were not different between normal and untreated diabetic or lysine-treated diabetic rats; however, the creatinine clearance was significantly higher in all groups of diabetic rats (normal 0.45 +/- 0.09 vs. diabetic 2.02 +/- 0.39 ml/min; p < 0.001). The data suggest that early rather than late treatment is more beneficial in reducing nonenzymatic glycation of collagen, although both treatments significantly reduced albuminuria. There was no nephrotoxicity as assessed by plasma creatinine levels or creatinine clearances. These beneficial effects occurred independent of changes either in blood pressure or plasma insulin concentration.     

Effects of melatonin on lipid peroxidation and antioxidant enzymes in streptozotocin-induced diabetic rat testis

Aim:To examine the effects of melatonin treatment on lipid peroxidation(LPO)and the activities of antioxidantenzymes in the testicular tissue of streptozotocin(STZ)-induced diabetic rats.Methods:Twenty-six male rats wererandomly divided into three groups as follows:group Ⅰ,control,non-diabetic rats(n=9);group Ⅱ,STZ-induced,untreated diabetic rats(n = 8);group Ⅲ,STZ-induced,melatonin-treated(dose of 10 mg/kg-day)diabetic rats(n=9).Following 8-week melatonin treatment,all rats were anaesthetized and then were killed to remove testes from thescrotum.Results:As compared to group Ⅰ,in rat testicular tissues of group Ⅱ,increased levels of malondialdehyde(MDA)(P<0.01)and superoxide dismutase(SOD)(P<0.01)as well as decreased levels of catalase(CAT)(P<0.01)and glutathione peroxidase(GSH-Px)(P>0.05)were found.In centrast,as compared to group Ⅱ,in rat testiculartissues of group Ⅲ,levels of MDA decreased(but this decrease was not significant,P>0.05)and SOD(P<0.01)aswell as CAT(P<0.05)increased.GSH-Px was not influenced by any of the treatment.Melatonin did not signifi-cantly affect the elevated glucose concentration of diabetic group.At the end of the study,there was no significantdifference between the melatonin-treated group and the untreated group by means of body and testicular weight.Conclusion:Diabetes mellitus increases oxidative stress and melatonin inhibits lipid peroxidation and might regulatethe activities of antioxidant enzymes of diabetic rat testes.(Asian J Androl 2006 Sep;8:595-600)     

Antinociceptive effects of combination of Tramadol and Acetaminophen on painful diabetic neuropathy in streptozotocin-induced diabetic rats

ObjectiveThe purpose of this study was to establish the streptozotocin (STZ)-induced diabetic model with rats and investigate the antinociceptive effect of combination of Tramadol (TR) and Acetaminophen (NAPA) on the animal model for the first time.MethodsDiabetic model was induced by a single injection of STZ (60 mg/kg, intraperitoneal). Nociceptive thresholds were measured by means of electronic von Frey test, hot-plate test, and tail-flick test. On the 28th day of diabetes induction, diabetic rats with significant hyperalgesia were randomly divided into three groups: TR, NAPA, and TR-NAPA combination group. Each group was randomly divided into four subgroups. Three geometric series of drugs were given to each group respectively. Antinociceptive effects of the drugs were assessed at 15, 30, 60, 120, and 180 minutes after drug administration. 50% Maximum antinociceptive effect of each drug was determined by probit analysis, whereas interaction between TR and NAPA was evaluated by isobolographic analysis.ResultsHyperalgesia, along with hyperglycemia, developed 4 days after STZ injection and persisted at all tested time points until 28 days. TR, NAPA, and TR-NAPA combination administration all produced dose-dependent antinociceptive effects. Isobolographic analysis showed a significant deviation of TR/NAPA 50% maximum antinociceptive effect (in tail-flick test, but not in von Frey test) from the additive line.ConclusionsCombination of the two drugs produces an additive antinociceptive effect in tail-flick test, whereas probable additive antinociceptive effect in von Frey test in painful diabetic neuropathy rats.     

The role of adrenomedullin and receptors in glomerular hyperfiltration in streptozotocin-induced diabetic rats

BACKGROUND: Since adrenomedullin (AM) elicits vasodilatation by binding to specific AM receptors consisted of calcitonin-receptor-like receptor (CRLR)/receptor-activity-modifying protein 2 (RAMP2) or CRLR/receptor-activity-modifying protein 3 (RAMP3) on endothelial cells and stimulating nitric oxide production, AM possibly involves in glomerular capillary dilatation in early phase of diabetic nephropathy. METHODS: Streptozotocin (STZ)-induced diabetic Sprague-Dawley rats at 4 weeks after the injection were employed for expression studies of AM, RAPM2, and RAMP3. The measurement of AM peptide levels in kidney tissue, plasma, and urine was performed. Human aortic endothelial cells (HAEC) were used to investigate functional link between glucose-induced AM production and nitric oxide release. RESULTS: STZ rats showed glomerular hypertrophy and increased urinary NO2- and NO3- excretion. By Northern blot analyses, AM and RAPM2 mRNAs significantly increased in the kidneys of STZ rats, while RAMP3 mRNA was not altered. In STZ rats, AM peptide was actively secreted into urine (1280 +/- 360 fmol/day vs. control 110 +/- 36 fmol/day). AM peptide was mainly detected on cortical and medullary collecting duct cells in control rat kidneys and AM peptide and mRNA were up-regulated on afferent arterioles and glomeruli of STZ rats. RAMP2 expression was detected on afferent arterioles and not in glomeruli in control rats and it was up-regulated on glomerular endothelial cells in STZ rats. In HAEC culture, d-glucose stimulated AM and nitric oxide production and they were suppressed by addition of AM antisense oligodeoxynucleotides. CONCLUSION: Up-regulated expression of AM and RAMP2 in afferent arterioles and glomeruli may be related to selective dilatation of glomerular capillary in acute phase of type 1 diabetes.