Noninvasive delayed limb ischemic preconditioning in rats increases antioxidant activities in cerebral tissue during severe ischemia-reperfusion injury.

BACKGROUND: To study the protection offered by noninvasive delayed limb ischemic preconditioning (NDLIP) against cerebral ischemia reperfusion (I/R) injury in rats. MATERIALS AND METHODS: Healthy male Wistar rats were randomly divided into four groups. The delayed protection offered by NDLIP was estimated in light of changes in the neural behavior marker and cerebral tissue antioxidative ability. Neurological functions were studied by observing neural behavior. Total superoxide dismutase (T-SOD), manganese-superoxide dismutase (Mn-SOD), glutathione peroxidase (GSH-PX), and xanthine oxidase (XOD) activity in cerebral tissue and malonaldehyde (MDA) content were detected using a spectrophotometer. Mn-SOD mRNA was measured by the reverse transcription polymerase chain reaction method. RESULTS: Cerebral infarct size was diminished in the early cerebral ischemia preconditioning (ECIP)+I/R and NDLIP+I/R groups compared with the I/R group (P < 0.05). The cortical and hippocampal antioxidant enzyme activity and Mn-SOD expression were increased in the ECIP+I/R and NDLIP+I/R groups. In contrast, the cortical and hippocampal XOD activity and MDA content decreased in the ECIP+I/R and NDLIP+I/R groups. CONCLUSIONS: NDLIP decreased cerebral infarct size, increased cerebral antioxidative ability after I/R injury, and decreased peroxidative damage. The antioxidative protection offered by NDLIP was as effective as that offered by ECIP.

[Limited sampling strategy to estimate pharmacokinetic parameters of orally administered metformin hydrochloride].

The present study was to estimate pharmacokinetic parameters of metformin hydrochloride in 20 Chinese healthy volunteers with a limited sampling strategy (LSS), which will provide scientific data for bioequivalence and clinical application. A single dose of metformin was administrated to 20 healthy volunteers. The concentration of metformin in whole blood was determined by validated high performance liquid chromatography (HPLC) method. Multi-linear regression analysis was performed to establish a model to estimate AUC(0-24 h) and Cmax of metformin by LSS method. The LSS models were validated by the Jackknife method. The result indicated: the linearity relationship between AUC(0-24 h) or Cmax and single concentration point was poor. Several models for metformin AUC(0-24 h) or Cmax, estimation were better (r2 > 0.9, P < 0.05). Validation tests indicated that most informative sampling points (C2, C6 for AUC(0-24 h), C1.5, C2 for Cmax) provided accurate estimations of these parameters. So, a multi-linear regression model for estimation pharmacokinetic parameters of metformin by using LSS method is feasible.

Limited sampling strategy in rats to predict the inhibited activities of hepatic CYP3A.

The present study was undertaken in order to evaluate feasibility of a limited sampling strategy (LSS) to predict the systemic clearance of midazolam (MDZ), which is a hepatic CYP3A activity phenotyping probe. Groups of rats pretreated with or without serial doses of ketoconazole, which is a selective inhibitor on CYP3A, were used as training set. Linear regression analysis and a Jack-knife validation procedure were performed based on plasma MDZ concentrations at specific time points after sublingual vein injection of MDZ to establish the most informative LSS equations for accurately estimating the clearance of MDZ. Another group of rats in the same setting was used as the validation set to confirm the individual values of estimated clearance (Clest) that were derived from the predictive equations developed in the training set. LSS that were derived from one, two or three sampling times, namely 90 min, 60-90 min, 30-60-90 min and 30-60-120 min, gave the best correlation and acceptable errors between the values of observed clearance (Clobs) and Clest and were chosen to evaluate hepatic CYP3A activity. Our results supported the hypothesis that using limited plasma sampling is simpler than the usual method of estimating CYP3A phenotyping by predicting the systemic clearance of MDZ when the hepatic activity of CYP3A is reduced in the rat. This experimental design offers opportunities to reduce animal use in the study of drug metabolism.

[A limited sampling strategy of phenotyping probe midazolam to predict inhibited activities of hepatic CYP3A in rats].

The present study was to evaluate feasibility of a limited sampling strategy (LSS) in the prediction of inhibited hepatic CYP3A activity with systemic clearance of midazolam (MDZ), a hepatic CYP3A activity phenotyping probe. Rats were pretreated with a serial doses of ketoconazole, a selective inhibitor on CYP3A. Blood samples were collected and detected for MDZ at specified time points after intravenous injection of MDZ. Stepwise regression analysis and a Jack-knife validation procedures were performed in one group of rats as training set to establish the most informative LSS model for accurately estimating the clearance of MDZ. Another group of rats with same treatment was used as validation set to estimate the individual clearance based on predictive equations derived from the training set. Bland-Altman plots showed a good agreement between the systemic clearance calculated from DAS (CLobs) and corresponding parameter that was derived from three LSS models (CLest). LSS models derived from two or three sampling time points, including 60, 90 min, 30, 60, 90 min and 30, 60, 120 min, exhibited a good accuracy and acceptable error for estimating the CLobs of MDZ to evaluate hepatic CYP3A activity, especially the 60, 90 min LSS model is most accurate and convenient. The results supported that limited plasma sampling to predict the systemic clearance of MDZ is easier than the usual method for estimating CYP3A phenotyping when the hepatic activity of CYP3A is reduced in the rat. The present study provided theoretical basis and laboratory evidence for LSS to clinically evaluate metabolizing function of liver and

Non-invasive limb ischemic pre-conditioning reduces oxidative stress and attenuates myocardium ischemia-reperfusion injury in diabetic rats.

This study was to explore whether repeated non-invasive limb ischemic pre-conditioning (NLIP) can confer an equivalent cardioprotection against myocardial ischemia-reperfusion (I/R) injury in acute diabetic rats to the extent of conventional myocardial ischemic pre-conditioning (MIP) and whether or not the delayed protection of NLIP is mediated by reducing myocardial oxidative stress after ischemia-reperfusion. Streptozotocin-induced diabetic rats were randomized to four groups: Sham group, the I/R group, the MIP group and the NLIP group. Compared with the I/R group, both the NLIP and MIP groups showed an amelioration of ventricular arrhythmia, reduced myocardial infarct size, increased activities of total superoxide dismutase (SOD), manganese-SOD and glutathione peroxidase, increased expression of manganese-SOD mRNA and decreased xanthine oxidase activity and malondialdehyde concentration (All p < 0.05 vs I/R group). It is concluded that non-invasive limb ischemic pre-conditioning reduces oxidative stress and attenuates myocardium ischemia-reperfusion injury in diabetic rats.

[Study on ultrastructure of cardioprotection of ramipril against ischemia/reperfusion injury in diabetic rats].

AIM: To investigate the effects of ramipril on myocardial ischemia/reperfusion injury in diabetic rats, and to explore its mechanism according to the observation on myocardial ultrastructure. METHODS: Streptozotocin induced diabetic rats were divided randomly into three groups (n = 16): ischemia/reperfusion (I/R), ischemic preconditioning (IPC) and ramipril (RAM) group. Rats in RAM group were administered by RAM(1 mg x kg(-1) x d(-1)) orally for 4 weeks, the others were administered by normal saline. Then all rats were subjected to myocardial ischemia/ reperfusion injury. Rats in IPC group were preconditioned before ischemia. The ECG and the infarct size were examined. The changes of myocardial morphology were examined by light and electron microscopes. RESULTS: Compared with I/R group, the elevation of ST segment and the incidence of ventricular tachycardia and ventricular fibrillation during ischemia were significantly decreased, the infarct size at the end of reperfusion was remarkably reduced, the myocardial morphology were significantly improved, special structure of myofilaments and mitochondria remained clearly, blood vessels were unobstructed, injury of endothelium were decreased in PC and RAM groups. CONCLUSION: Ramipril administered for 4 weeks induces myocardial protection in diabetic rats, which is similar to that of IPC. The mechanism may be involved in protection of cardiocytes and mitochondria, and improvement of endothelial function.

[Effects of noninvasive limb ischemic preconditioning on anti-stress ability in mice].

AIM: To explore the effects of noninvasive limb ischemic preconditioning on the anti-stress ability in mice. METHODS: Mice were divided into: normal group, control group, preconditioning group and drug group. Hypoxia tolerance test, swimming with weight loading, cold tolerance test and thermostable test were performed, and tolerance time in all the stringent state were observed. SOD activity of serum in hypoxia tolerance test and lactic acid of serum in swimming with weight loading test were determined. RESULTS: The time of hypoxia tolerance in preconditioning group was markedly increased, and SOD activity of preconditioning group mice was significantly higher than those of control group, while they were both shorter than drug group. The average time of swimming in preconditioning group was markedly increased and the level of increasing the swimming time of preconditioning was the same as caffeine. Preconditioning could increase the survival time on high temperature markedly, and there was no significantly difference in the level of increasing the survival time between preconditioning group and chlorpromazine group. Preconditioning could increase the time of cold tolerance markedly compared with normal group. CONCLUSION: Noninvasive limb ischemic preconditioning can improve the ability of anti-hypoxia, anti-fatigue, thermoresistance and cold-resistance in mice.