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OBJECTIVE: To explore different doses of sodium(s)-2-(dithiocarboxylato((2R,3R,4R,5R,6R)-2,3,4,5,6-pentahydroxyhexyl) amino)-4-(methylthio) butanoate(GMDTC) for removing cadmium. METHODS: Thirty-five male New Zealand rabbits were randomly divided into blank control group,GMDTC high dose control group,model control group,ethylene diamine tetraacetic acid(EDTA) control group and GMDTC low,medium and high dose groups,five rabbits in each group. The blank control group and GMDTC high dose control group were given 0. 90% normal saline solution intravenously; model control group,EDTA control group and GMDTC low,medium and high dose group were given 2 μmol/kg of cadmium chloride(CdCl_2) and 40 μmol/kg of β-mercaptoethanol mixed solution intravenously,5. 0mL/kg body weight(bw),once a day for five days. On the forty-one day of the experiment(the fist day of GMDTC treatment),the control group and the model control group were injected 0. 90% normal saline solution 250 mL via ear vein,the EDTA control group was given EDTA solution at the dose of 93. 5 mg/kg bw with 250 mL 0. 90% normal saline solution,also via ear vein; the GMDTC high dose control group,and the GMDTC low,medium and high dose groups were given 250 mL GMDTC solution at the concentration of 108.0,12.0,36.0 and 108. 0 mg/kg bw with 0. 90% normal saline by intravenous infusion,once a day,6 times a week for four consecutive weeks. The urine β_2-microglobulin(MG),renal cadmium,blood cadmium,and urinary cadmium before and after the treatment were detected. RESULTS: The body weight of New Zealand rabbits increased with the increasing feed time(P < 0. 01). The levels of β_2-MG before treatment increased in model control group,EDTA control group,GMDTC low,medium and high dose groups than that in the blank control group(P < 0. 01). The levels of renal cadmium after treatment in GMDTC medium and high dose groups decreased compared with those in the blank control group and EDTA control group respectively(P < 0. 05). The blood cadmium after treatment in EDTA control group,GMDTC low,medium and high dose groups were decreased compared with those before treatment in the same group respectively(P < 0. 05),meanwhile decreased than the blood cadmium after treatment in the model control group respectively(P < 0. 05). The blood cadmium after treatment had not a statistically significant difference among the EDTA control group,GMDTC medium and high dose groups(P < 0. 05). At all the time points(1,6,8,13,15,20,22 and 28 days after treatment),the urinary cadmium after treatment in EDTA control group and the three GMDTC dose groups increased compared to the model control group at the same time(P < 0. 05). The urinary cadmium after treatment increased with GMDTC dose increased at the other six time points,expect on 20 and 22 days after treatment(P < 0. 05). The blood cadmium removal rates after treatment were 70. 06%,74. 86% and 78. 05% and the renal cadmium removal rates were 14. 27%,27. 95% and 61. 24% in GMDTC low,medium and high dose groups,respectively. CONCLUSION: The intravenous infusion of GMDTC at the dose of 108. 0 mg/kg bw effectively removed cadmium in cadmium poisoning rabbit. This dose had no obvious toxic effect and was equivalent to human dose of 36. 0mg/kg bw which meets the requirement of new drug property.
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The value of snake venom polypeptides in clinical application has drawn extensive attention,and the development of snake polypeptides into new drugs with anti-tumor,anti-inflammatory,antithrombotic,analgesic or antihypertensive properties has become the recent research hotspot.With the rapid development of molecular biology and biotechnology,the mechanisms of snake venom polypeptides are also gradually clarified.Numerous studies have demonstrated that snake venom polypeptides exert their pharmacological effects by regulating ion channels,cell proliferation,apoptosis,intracellular signaling pathway,and expression of cytokine as well as binding to relevant active sites or receptors.
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Objective To investigate the role of endogenous nitric oxide synthase (NOS) inhibitor asymmetric dimethylarginine (ADMA) in the contractile dysfunction of skeletal muscle in diabetic rats and on which the therapeutic effects of L-Arginine.Methods Type 2 diabetic rats were induced by high fat diet and a single intraperitoneal injection of streptozotocin (STZ,30 mg/kg),followed by high fat diet for 8 weeks.Specific twicth tension and specific tetanic tension of soleus (SOL) and extensor digitorum longus (EDL) isolated from control and diabetic rats were detected by electric stimulation to reflect contractile function of skeletal muscle.ADMA content of skeletal muscle was analyzed by enzyme linked immunosorbent assay (ELISA),and activities of dimethylarginie dimethylaminohydrolase (DDAH) and NOS,NO content were measured by colorimetry.The protein expression of ADMA synthetase protein arginine methyl transferase 1 (PRMT1) and ADMA hydrolase DDAH and NOS were determined detected by Western blotting.Oral glucose tolerance test and protein expressions of phosphorylated insulin receptor substrate 1 (p-IRS-1) and protein kinase B (p-Akt) as well as the membrane transportation of glucose transporter 4 (Glut4) were measured to reflect insulin resistance.Results In comparison with control rats,specific twicth tension and tetanic tension of SOL and EDL in diabetic rats were significantly decreased (P ＜ 0.01),indicating the contractile dysfunction.Increased ADMA content (P ＜ 0.05),decreased DDAH and NOS activities as well as NO content (P ＜ 0.01) in comparison with up-regulated protein expression of PRMT1 and down-regulated protein expression of DDAH,endothelial NOS (eNOS) and neuronal NOS (nNOS) (P ＜ 0.05) were observed in the skeletal muscle of diabetic rats compared to control rats,indicating that the pathway of PRMT1/ADMA/DDAH/ NOS/NO was disordered in the skeletal muscle of diabetic rats.Furthermore,the glucose tolerance,both IRS-1 and Akt protein phosphorylation as well as the membrane translocation of Glut4 were decreased (P ＜ 0.05),indicating the insulin resistance in diabetic rats.Treatment with L-Arginine for 8 weeks not only significantly improved the contractile dysfunction but also reversed the disorder of ADMA signaling pathway and insulin resistance in skeletal muscle of diabetic rats compared to untreated diabetic rats.Conclusions The accumulation of endogenous NOS inhibitor ADMA contributes to the contractile dysfunction of skeletal muscle in diabetic rats,the underlying mechanism may be related to insulin resistance.
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AIM This study was designed to investigate the effect of aminoguanidine, an inhibitor of the glycosylated proteins formation, on the impairment of endothelium dependent relaxation induced by advanced glycation end products (AGE) in isolated rat thoracic aorta and its possible mechanisms. METHODS Exogenous glycosylated bovine serum albumin (AGE BSA) was prepared. Aortic rings were exposed to AGE BSA for 60 min to induce the impairment of endothelium dependent vasodilatation. In the drug treated groups, aortic rings were incubated with drug for 15 min and then exposed to AGE BSA for another 60 min in the presence of the drug. Vasodilator responses to acetylcholine (ACh) or sodium nitroprusside (SNP) of aortic rings were measured by isometric tension recording after drug treatment. RESULTS AGE BSA significantly inhibited the endothelium dependent relaxation in response to ACh, but did not affect endothelium independent relaxation in response to SNP. Pre incubation of aortic rings with aminoguanidine(50～500 ?mol?L -1 ) for 15 min and co incubation of aortic rings with AGE BSA for another 60 min markedly attenuated the inhibition of endothelium dependenet relaxation induced by AGE BSA in a dose dependent manner. Superoxide diamutase (SOD, 2?10 5 U?L -1 ), a scavenger of superoxide anions, also prevented the inhibition of endothelium dependent relaxation, which is similar to the effect of 500 ?mol?L -1 aminoguanidine. Furthermore, aminoguanidine (500 ?mol?L -1 ) also reversed impairment of endothelium dependent relaxation of rat aortic ring induced by endogenous oxygen free radicals generated by diethyldithiocarbamate (DETC, 10 ?mol?L -1 ) via inhibiting intracellular SOD. CONCLUSION Aminoguanidine can protect rat aortic endothelium against damage due to AGE BSA, and the beneficial effect of aminoguanidine may relate to its antioxidant properties.
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AIM To determine the relationship between the elevation of endogenous inhibitor of nitric oxide synthase (NOS)N G,N G-asymmetric dimethylarginine (ADMA) and metabolic control in diabetic rats. METHODS Diabetes was induced in Sprague-Dawley rats by a single intraperitoneal injection of streptozotocin. At 72 h after injection, half of diabetic rats received insulin treatment for 8 weeks (20 U?kg -1?d -1,ih, bid). Serum levels of ADMA were measured by high-performance liquid chromatography. Thoracic aortic rings from non-diabetic age-matched control, untreated diabetic, and insulin-treated diabetic rats were tethered in isolated organ baths,contracted with 1 ?mol?L -1 phenylephrine, and challenged with either the endothelium-dependent vasodilator acetylcholine or the endothelium-independent vasodilator sodium nitroprusside. Serum concentrations of glucose, glycosylated serum protein, and malondialdehyde, derived from lipid peroxidation were also examined to estimate metabolic control.RESULTS Serum levels of ADMA significantly elevated in untreated diabetic rats compared with control rats. This elevation of ADMA was accompanied by impairment of relaxation response to acetylcholine but not sodium nitroprusside in aortic rings. Chronic insulin treatment not only prevented the elevation of serum ADMA, but also improved the impaired endothelium-dependent relaxation in diabetic rats. Serum levels of glucose, glycosylated serum protein, and malondialdehyde were significantly increased in parallel with the elevation of ADMA in untreated diabetic rats compared with control rats. These parameters were normalized after diabetic rats received insulin treatment. CONCLUSION These results provide the first evidence that the elevation of endogenous inhibitor of NOS in streptozotocin-induced diabetic rats is close related to metabolic control of the disease.