Long-term changes in the diabetic state induced by different doses of streptozotocin in rats

The long-term effects of different doses (0, 25, 35, 45, 55, 65 and 100 mg/kg) of streptozotocin (STZ) in male Wistar rats had been followed over a 16 week period. The weight-gain curve and the epididymal fat pad weight were significantly different (P less than 0.05) from control after 1 week with the 65 and 100 mg/kg doses and after 4 weeks with the 45 and 55 mg/kg doses; there were no significant changes with the 25 and 35 mg/kg doses even after 16 weeks. An i.v. glucose tolerance test (0.5 g/kg) was performed at 1, 4 or 16 weeks after the injection of STZ. The basal levels of glucose were significantly elevated (P less than 0.05) after 1 week with the greater than or equal to 55 mg/kg doses, and after 16 weeks with the greater than or equal to 45 mg/kg doses; there was also an overall increase in the basal glucose levels between 1 and 16 weeks in rats treated with the greater than or equal to 45 mg/kg doses. The basal insulin levels were significantly decreased (P less than 0.05) after 1 week with the greater than or equal to 65 mg/kg doses, after 4 weeks with the greater than or equal to 55 mg/kg doses and after 16 weeks with the greater than or equal to 35 mg/kg doses. The insulin peak 2 min after the glucose load was significantly less (P less than 0.05) after 1 week with the greater than or equal to 35 mg/kg doses and after 16 weeks with the greater than or equal to 25 mg/kg doses. The use of an insulinogenic index to assess the insulin secretory capacity showed a significant decrease (P less than 0.05) for the greater than or equal to 35 mg/kg doses at each tested time; with the 45 mg/kg dose, there was a further significant decrease (P less than 0.01) between the first and sixteenth week. The present long-term studies showed that there is a progressive deterioration in the glucose tolerance and insulin secretion after the injection of different doses of STZ. Furthermore, changes in glucose-insulin interrelationships over time suggest that the insulin insensitivity previously described in STZ diabetic rats might be only an early transient phenomenon.     

Hepatocellular neoplasms induced by low-number pancreatic islet transplants in streptozotocin diabetic rats.

We have previously demonstrated in short-term experiments that altered hepatocytes in liver acini draining the blood from intraportally transplanted pancreatic islets in streptozotocin-induced diabetic rats with mild persisting diabetes resemble those in preneoplastic foci of altered hepatocytes. We now present the results of long-term studies (up to 22 months) in this animal model. Glycogen-storing foci (which were the first parenchymal alteration observed some days after transplantation) persisted at least for 6 months, when the first mixed-cell foci and the first hepatocellular adenoma emerged. After 15 to 22 months, 86% of the animals exhibited at least one hepatocellular adenoma and four animals (19%) showed a hepatocellular carcinoma. The transplants were found in a close spatial relationship with the preneoplastic foci and the hepatocellular neoplasms. The mitotic indices, the 5-bromo-2'-desoxyuridine labeling indices and the apoptotic indices showed significant differences between the unaltered liver parenchyma, different types of preneoplastic foci, and hepatocellular neoplasms. The immunohistochemical expression of transforming growth factor-alpha increased during the stepwise development from glycogen-storing liver acini to hepatocellular carcinomas. Hepatocarcinogenesis in this new animal model is probably due to the hormonal and growth-stimulating effects of insulin secreted by the intraportally transplanted islets of Langerhans in diabetic rats.     

The morphology of diabetic nephropathy in experimental diabetes induced by low doses of streptozotocin

Kidneys of 16 Wistar rats were examined by light and electron microscopy, immunofluorescence and biochemically for the transamidinase activity at various periods of experimental diabetes induced by the fractionated intraperitoneal administration of low (40 mg/kg) doses of streptozotocin. 18 rats of the same age and sex served as control. This model of diabetes is characterized by a gradual decrease of the serum immunoreactive insulin, increase of hyperglycemia, the presence of "insulitis" 19 days after the beginning of the experiment and the development of nephropathy in the genesis of which immune mechanisms might participate. Transamidinase activity correlated with the alterations of renal tubuli. The conclusion is made on the possibility of using this model of experimental diabetes for studying the pathogenetic mechanisms of renal lesions in diabetes; transamidinase activity allows one to evaluate the nephron function in diabetic nephropathy.     

Alteration of the proteome profile of the pancreas in diabetic rats induced by streptozotocin

Type 1 diabetes mellitus (T1DM) is receiving increased attention. To obtain a better understanding of the mechanism underlying T1DM, we performed a proteomic study on a rat model induced by streptozotocin. Pancreatic proteins were separated by two-dimensional gel electrophoresis. Eighteen protein spots were differentially expressed (P<0.05) with 2-fold or more increased or decreased intensity in the diabetic rats as compared with controls, of which 11 protein spots were up-regulated and 7 protein spots were down-regulated. These protein spots were successfully identified by liquid chromatography-electrospray ionization tandem mass spectrometry. The 60 kDa heat shock protein, the carbonyl reductase 1 (Cbr1), the hydroxyacyl-CoA dehydrogenase, Δ(3,5),Δ(2,4)-dienoyl-CoA isomerase, the elongation factor 1-δ, the 26S protease regulatory subunit 7 and the transitional endoplasmic reticulum ATPase were up-regulated, while the 78 kDa glucose-regulated protein, peroxiredoxin 4 and plakoglobin were down-regulated. The expression change of Cbr1 which is closely related to diabetic complications was further validated by western blotting. Our results and those of the bioinformatics analysis suggest that oxidative stress, the Wnt pathway, fatty acid degradation and glucose transport may be closely related to T1DM.     

链脲佐菌素诱导MSG大鼠糖尿病心脏病模型的研究

目的:探讨腹腔注射链脲佐菌素(Streptozotocin,STZ)诱导L-谷氨酸钠(Monosodium glutamate,MSG)肥胖大鼠建立糖尿病心脏病模型。方法:选用新生SD大鼠随机分为两组:MSG组和正常对照组(NS组)。MSG组新生大鼠自出生第2d起颈部皮下注射L-谷氨酸钠5g·kg-1,隔天一次,共三次;正常对照组于皮下注射等体积无菌注射用水。MSG组于6周龄时再随机分为4个小组,腹腔注射链脲佐菌素0mg·kg-1,20mg·kg-1,30mg·kg-1,40mg·kg-1。于注射STZ 4w后测定各心脏血流动力学相关指标,同时取血测定其胰岛素水平及血液脂质等指标。结果:注射STZ 4w后,MSG组大鼠Lee’s指数显著增加,心脏指数明显降低,血浆高密度胆固醇(HDL)、低密度胆固醇(LDL)升高,收缩压(SBP)、舒张压(DBP)、平均动脉压(MAP)、心率(HR)、左心室收缩压(LVSP)、左心室内压最大上升速率(+dp/dt)、下降速率(-dp/dt)均显著升高,心电图显示其Q-T间期缩短,与对照组比较有统计学差异。MSG+STZ 30mg·kg-1组大鼠SBP、DBP、MAP、HR、+dp/dt、-dp/dt均显著降低,与MSG组比较有统计学差异。MSG+STZ 40mg·kg-1组大鼠SBP、DBP、MAP、HR、LVSP、+dp/dt、-dp/dt均显著降低,Lee’s指数降低,胰岛素浓度降低,血糖水平及心脏指数升高,血浆LDL水平降低,Q-T间期延长,与MSG组比较有统计学差异。结论:研究表明MSG大鼠在6周龄时腹腔注射STZ 40mg·kg-1,有利于糖尿病心脏病模型的建立,为研究、开发防治2型糖尿病心脏病的新药提供了一种良好的动物模型。     

真武汤对链脲佐菌素所致大鼠糖尿病肾病的保护作用

 目的：探讨真武汤对糖尿病大鼠肾脏的保护作用及机制。方法：腹腔注射链脲佐菌素(STZ)建立糖尿病肾病大鼠模型,将成模大鼠随机分为糖尿病肾病(DN)模型组和真武汤治疗组（真武组）,另设正常组。采用生化、HE染色观察真武汤对糖尿病肾病大鼠肾功能、肾组织形态学变化及脂质过氧化相关参数的作用;采用蛋白免疫印迹方法探讨真武汤对肾组织α-平滑肌肌动蛋白（α-SMA）和NF-κB表达的影响。结果：模型组大鼠肾系数、24 h尿蛋白定量、血尿素氮、肌酐、血糖和丙二醛(MDA)均显著升高(P<0.05),体重、超氧化物歧化酶(SOD)及诱导型一氧化氮合酶（iNOS）显著降低(P<0.05);真武组大鼠的肾系数、24 h尿蛋白、尿素氮、肌酐、血糖和MDA明显低于模型组(P<0.05),iNOS显著高于模型组（P<0.05）;模型组大鼠肾小球肥大、毛细血管基底膜增厚,系膜基质增生,肾小管上皮细胞空泡样变,可见蛋白管型;真武组病变轻于模型组。模型大鼠肾组织α-SMA及NF-κB蛋白的水平明显高于正常组（P<0.05）,真武组大鼠肾组织α-SMA及NF-κB蛋白水平明显低于模型组（P<0.05）。结论：真武汤能减轻糖尿病肾病肾脏局部氧化应激反应,改善糖尿病肾病大鼠肾功能,减轻病理损伤,其发挥肾脏保护作用可能与抑制α-SMA及NF-κB蛋白的表达有关。     

Alternations in free radical erythrocyte-defense mechanisms in streptozotocin induced diabetic rats - effect of antioxidant treatment.

The activities of superoxide dismutase, glutathione peroxidase and the contents of glutathione, malondialdehyde were examined in erythrocytes of streptozotocin induced diabetic rats. The above mentioned antioxidant systems of erythrocyte were determined after treatment of diabetic rats with superoxide dismutase, trolox, catalase and allopurinol. In erythrocytes of streptozotocin induced diabetic rats the activities of superoxide dismutase, glutathione peroxidase as well as the levels of reduced glutathione were lower whereas the contents of oxidized glutathione and malondialdehyde were higher than in controls. Superoxide dismutase and trolox treatment of diabetic rats resulted in an increase of erythrocyte glutathione peroxidase activities and in reduced glutathione levels. However the levels of oxidized glutathione decreased after treatment of diabetic rats with superoxide dismutase and trolox. Catalase and allopurinol administration did not have any influence on the activities of the investigated enzymes nor on the levels of glutathione in diabetic rats. The antioxidants under study did not cause any changes in the increased level of malondialdehyde in erythrocytes.     

Ultrastructure of the macula densa in streptozotocin diabetic rats

Morphometric analyses of the macula densa in streptozotocin diabetic rats have revealed, that the volume density of the large lateral intercellular spaces, which are present in normal animals between the macula densa cells, decreases significantly in magnitude from 8.7 to 1.5% in diabetic animals. The volume density of cytoplasmic glycogen in the macula densa cells increases significantly from 5.4% in the controls to 14.8% in the diabetic animals, but the total volume density of mitochondria is the same in the two groups. The contact area between macula densa cells and the Goorgmaghtigh cells is increased by 38% in the diabetic animals compared with controls. The structural abnormalities in the macula densa in response to diabetes might be considered a structural counterpart to the alterations in the tubuloglomerular feedback mechanism and the increase in glomerular filtration rate in diabetes.     

Study of histochemical and biochemical changes in the liver of rats induced by high doses of isoprenaline.

The aim of the present work was to study by means of histochemical and chemical methods the 7-day course of changes in carbohydrate metabolism in the liver of male rats induced by a single dose of isoprenaline of 50 mg/kg administered subcutaneously. A statistically significant reduction was seen both in the level of free glycogen and lactate within 24 hours. The decrease of pyruvate level was not so marked. At the same time, there was increased, and within the hepatic lobules also extended activity of enzymes catalyzing glycogenolysis, i.e. alpha-glucan phosphorylase and particularly the branching Q-enzyme, glucose-6-phosphatase and LDH, whereas the level of malate and activity of SDH, which are constituents of the Krebs cycle, were found to be reduced. Cytochrome oxidase activity was changed after 24 hr compared to the controls. The obtained results indicate that an extensive glycogenolysis occurs in the liver of rats in the 24 hr following s.c. administration of isoprenaline, the major part of liver glycogen being degraded through glucose-6-phosphate to blood glucose and its metabolism via the Krebs cycle reduced. The observed metabolic changes are of reversible character and tend to normalize over the 2nd and 3rd day following isoprenaline administration.     

Studies on a stable,mild diabetes induced by streptozotocin in rats.

A stable, mild diabetes in rats maintained on a normal laboratory diet was induced by a single i.p. injection of streptozotocin. Irreversible damage of the pancreatic islet B cells was complete by 3 days after treatment and plasma immunoreactive insulin was undetectable throughout the remaining 12-week period of investigation. The diabetes was characterized by hyperglycaemia of over 30 mM and a constant elevation of plasma alanine and branch-chain amino acids throughout the 12 weeks. In contrast to severe diabetes, plasma free fatty acids rose only gradually from normal values to reach 1.5 mM by week 12, ketone bodies were only slightly elevated (0.7 mM maximum) and liver glycogen was maintained throughout at around 30% of the normal, fed value. Starvation for up to 40 h caused only slight changes (in contrast with non-diabetic animals) and in particular no changes in free fatty acid or ketone bodies were found. These metabolic results are discussed in relation to the mechanisms thought to control those processes.     

α-硫辛酸减轻STZ所致大鼠胰岛β细胞损伤

链脲佐菌素(streptozotocin,STZ)对胰岛β细胞的特异毒性是自由基介导的.а-硫辛酸(a-lipoic acid,ALA)是有效抗氧化剂.本研究观察ALA对STZ所致胰岛B细胞损伤的保护,并探讨其机制.     

Sodium fusidate ameliorates the course of diabetes induced in mice by multiple low doses of streptozotocin

We studied the effects of the immunosuppressant sodium fusidate (fusidin) on murine immunoinflammatory diabetes mellitus (DM) induced by multiple low doses of streptozotocin (SZ). Fusidin was given by gavage to three strains of mice (C57KsJ, C57BL/6, CD1) at doses 10 or 100 mg/kg body weight every other day. The drug was administered as an early or late prophylactic regime starting either 1 day prior to the first or after the fifth and last injection of SZ. In both situations the largest dose of fusidin successfully reduced the clinical, chemical and histological signs of DM, the treated mice having significantly lower glycaemic values and milder (often absent) insulitis compared with sham-treated animals or controls given SZ alone. The antidiabetogenic effect was long-lasting as it was maintained up to 1 month after cessation of therapy. In contrast, fusidin prophylaxis failed to prevent development of hyperglycaemia acutely induced by one single and high (160 mg/kg) dose of SZ, which is a model of DM primarily due to the toxic action of SZ on the beta cells and does not involve immunopathogenetic mechanisms.On day 14 after SZ, fusidin markedly altered the circulating cytokine profile induced in vivo by ConA, reducing the levels of IFN-gamma, IL-2 and TNF-alpha and augmenting the level of IL-6. However, only the inhibitory effect of the drug on the synthesis/release of IFN-gamma seemed to be causally related to its capacity to counteract the SZ-induced DM. In fact, the disease was prevented by a neutralizing monoclonal antibody (mAb) against IFN-gamma, but not by anti-IL-2 receptor mAb, a soluble form of TNF-receptor type 1 or recombinant human IL-6. The prevention of disease by fusidin was also partly reversed by exogenously administered recombinant mouse IFN-gamma.The data provide further in-vivo evidence for the anti-diabetogenic and immunomodulatory properties of fusidin and indicate that this drug could have a role in prevention and treatment of human type 1 DM.     

Blood pressure and heart rate changes in streptozotocin diabetic rats, with special reference to postural hypotension.

Blood pressure and heart rate changes were recorded on supine or prone head-up tilt and on carotid artery occlusion in normal and streptozotocin diabetic rats (65 mg/kg). In general supine tilt induced a larger blood pressure fall, slower blood pressure recovery from the fall and larger heart rate fall than prone tilt, both in normal and diabetic rats. Heart rate recovery from the fall was slightly larger in prone than in supine tilt in normal rats. The blood pressure fall and heart rate fall accompanying the tilt were statistically larger in diabetic than in normal rats. Furthermore, blood pressure recovery from the fall was statistically more rapid and larger in normal than in diabetic rats. The exaggerated blood pressure fall with the tilt of diabetic rats might correspond to postural hypotension. Blood pressure rise and heart rate rise with carotid artery occlusion were smaller in diabetic than in normal rats. Blood pressure changes with cervical sympathetic or vagus stimulation were almost the same in normal and diabetic rats. However, in diabetic rats such cervical autonomic nerve stimulation produced larger heart rate changes than in normal rats.     

Glomerular renin angiotensin system in streptozotocin diabetic and Zucker diabetic fatty rats

Substantial evidence suggests that the intrarenal renin-angiotensin system (RAS) plays a role in the pathogenesis of diabetic nephropathy. Although the glomerular RAS is activated in the streptozotocin (STZ)-diabetic rat, the status of the glomerular RAS in the Zucker diabetic fatty (ZDF) rat, which is a commonly used genetic model of diabetes, is not known. Angiotensinogen (AGT), angiotensin II (Ang II), angiotensin converting enzyme (ACE), and angiotensin converting enzyme 2 (ACE2) were measured in glomeruli isolated from 4-week-old STZ-diabetic rats and 32-week-old ZDF rats. Glomerular injury was evaluated by histopathologic methods. Both STZ-diabetic and ZDF rats exhibited marked hyperglycemia and renal hypertrophy, but only ZDF rats demonstrated proteinuria and glomerulosclerosis. Glomerular AGT and Ang II levels were increased significantly in STZ-diabetic compared with nondiabetic control rats, accompanied by a reduction in ACE2 activity. In contrast, glomerular AGT, Ang II, and ACE2 were similar in ZDF rats and lean controls. ACE levels were not affected by diabetes in either diabetic model. In conclusion, the glomerular RAS is activated in the STZ diabetic rat but not in the ZDF rat despite a similar degree of hyperglycemia. The mechanism of nephropathy in the ZDF rat may involve factors other than hyperglycemia and RAS activation, such as hypertension and hyperlipidemia.     

Lack of cardiotoxic effect of isoproterenol in streptozotocin diabetic rats

Summary The well known cardiotoxic effect of isoproterenol (ISO) was investigated in normal and streptozotocin diabetic rats. Seven days after the subcutaneous injection of ISO (15 mg/kg) the hearts were perfusion fixed and 12 sections from each heart were stained (Masson's trichrome). ISO induced myocardial fibrosis was quantified at the light microscopic level according to established morphometric principles. Pulse rate and ST elevation were recorded by EEC (3 standard leads) before and after the ISO injection. Non-diabetic control animals showed marked fibrosis after ISO, but surprisingly the diabetic animals showed no fibrosis after ISO treatment. These findings were in accordance with an ISO induced ST elevation seen only among control animals although both groups showed the same degree of tachycardia. Insulin treatment prevented the protection against ISO and when streptozotocin was injected 24 h after the ISO a normal quantitative and qualitative appearance of the scar tissue was seen. It thus seems that streptozotocin diabetic rats are protected against the toxic effect of ISO, leaving the haemodynamic response unaffected. Which factor in the diabetic metabolism is reponsible for the present phenomenon is not known, but a defect in the signal transmission from the -receptor to the adenylcyclase is suggested as a possible explanation.     

糖尿病大鼠创面愈合过程中成纤维细胞增殖及Ⅰ型胶原合成减少

目的：观察链脲佐菌素诱导的大鼠糖尿病复合创伤修复过程中成纤维细胞增殖与胶原合成的变化。 方法： 实验采用Wistar大鼠112只，随机分对照组和模型组。模型组大鼠腹腔注射链脲佐菌素（STZ）55 mg/kg，3周后各组动物复合背部2.04 cm²全厚皮切除形成伤口。观察创面愈合时间和愈合率；采用HE染色和免疫组化法观察成纤维细胞和增殖细胞核抗原(PCNA)表达水平；采用苦味酸-天狼星红染色和图像分析技术观察创面Ⅰ、Ⅲ型胶原含量及Ⅰ/Ⅲ型比值。 结果： STZ诱发的糖尿病大鼠复合创伤后创面的愈合时间为(27.13±1.81)d，明显长于对照组（15.25±1.67）d，P<0.01；模型组在创伤第3、7和15 d创面愈合率明显低于对照组，分别P<0.01；在3、5、7和9 d模型组创面成纤维细胞数量和PCNA表达也明显少于对照组，分别P<0.05和P<0.01。两组创面在不同时点上Ⅰ型胶原分布均呈递增趋势，但对照组明显多于模型组，分别P＜0.05；尽管对照组在创伤3、7 d Ⅲ型胶原含量高于模型组，但在创伤3、7和11 d模型组Ⅰ/Ⅲ胶原比值都明显低于对照组，分别P＜0.01。 结论： STZ可能通过影响创面细胞增殖和创面胶原合成，从而导致创面愈合迟缓。     

链尿佐菌素制备糖尿病神经源性膀胱大鼠模型

目的对使用单次腹腔注射大剂量链尿佐菌素（STZ）制备糖尿病神经源性膀胱大鼠模型的方法进行探讨。方法使用随机分组的方法将30只SPF级健康雄性sD大鼠随机分成正常对照组（NC组）10只、糖尿病组（DM组）20只;给予糖尿病组大鼠单次腹腔注射链尿佐菌素（60mg／kg）,同时给予对照组大鼠相同剂量的柠檬酸钠缓冲液,3d后测空腹血糖,血糖≥16．7mmol／L大鼠入选为糖尿病组模型。后观察大鼠一般指标（精神、皮毛光泽度、血糖、体重、饮食量、饮水量等）,8周时取出膀胱测残尿量、膀胱湿重、行HE染色。结果3d后糖尿病组大鼠糖尿病成模率达到90％,8周后血糖值稳定,糖尿病组膀胱HE染色有明显病理改变。DM组中糖尿病大鼠模型的糖尿病神经源性膀胱大鼠模型成模率为100％。结论通过单次大剂量腹腔注射链尿佐菌素（60mg／kg）可快速制备稳定的糖尿病大鼠模型,且在此基础上诱导神经源性膀胱大鼠模型的成功率高,在8周时其成模率可达100％。是目前一种简便、快速获取稳定糖尿病神经源性性膀胱大鼠模型的方法。