Potentiating effect of rifampicin on methimazole induced hepatotoxicity in mice.

Methimazole (MMI) is a widely used drug for hyperthyroidism. However, its clinical use is associated with hepatotoxicity. Though the precise mechanism of hepatic damage is still far from clear, role of metabolic activation and reactive metabolites have been implicated. The present study was designed to investigate the role of enzyme induction in bioactivation based hepatotoxicity of methimazole in mice. Thirty male mice were randomly divided into five groups. Hepatotoxicity was induced by single intraperitoneal injection of methimazole (1000mg/kg). Pretreatment with rifampicin which is a potent enzyme inducer was carried out for 6 days prior to administration of methimazole. The extent of hepatic damage was determined by measuring serum alanine aminotransferase (ALT) and alkaline phosphatase (ALP) along with histopathological grading of liver samples. The elevated levels of biochemical markers by methimazole were potentiated by pretreatment with rifampicin. This potentiation of hepatic injury was also observed in liver histopathological examination. These findings suggest induction of microsomal enzymes as a potentiating factor of methimazole induced hepatotoxicity.

Alpha-tocopherol ameliorates nephrotoxicity associated with the use of colistin in rabbits.

The alarming rise in the rate of multi drug resistant, life threatening gram negative infections has brought renaissance in the use of Colistin for last two decades. The major constraint in its utilization is its nephrotoxicity. Therefore it is being underused which is favoring the development of resistance. This study assesses the prevention of nephrotoxicity associated with high and low toxic doses of Colistin by alpha-tocopherol. Thirty rabbits were randomly divided into five groups. Baseline serum urea, creatinine and electrolytes were estimated. A loading dose of colistin was given in the form of infusion followed by I.M injections for six days. In the preventive groups α-tocopherol was additionally given orally for two weeks. Rabbits were sacrificed 24 hours after the last dose. The kidney slides graded and statistically analyzed using "chi square". The results of serum analysis were compared using one way analysis of variance followed by post hoc tukey test. There was marked nephrotoxicity in high toxic group where as in low toxic group mild nephrotoxicity was evident. Alpha-tocopherol attenuated the renal insult in both the toxic groups. As damage induced by colistin is oxidative in nature, thus it was concluded that the protection offered by α- tocopherol is due to its antioxidant activity.

Ondansetron: A newer aspect of dose response relationship on ileal smooth muscles of rabbit.

There are several life threatening deadly diseases in our world but 'Cancer' out powers them all in recent years. Chemotherapy may be used on its own or an adjunct to other forms of therapy. Despite the advancement in cytotoxic drug therapy and supportive treatment almost 70% of patient suffer from chemotherapy induced nausea and vomiting (CINV). Ondansetron, a 5-HT(3) receptor antagonist has now become a gold standard in the treatment of chemotherapy induced nausea and vomiting. The central actions of ondansetron are well established but its peripheral actions are not well recognized. The aim of our study was to explore the peripheral actions of ondansetron. Experiments were performed in five groups (n=6) and ileal smooth muscles activity was recorded on power lab (USA). The effects of increasing concentrations of acetylcholine, serotonin & ondansetron alone was observed in first three groups. In the next two groups effects of acetylcholine and serotonin pretreated with fixed concentration (1ml) of ondansetron (10¯Ï– M)were studied. The maximum response obtained by acetylcholine served as a control for our study. Maximum response with acetylcholine was taken as 100% and with serotonin was 177 percent of control. Cumulative dose response curve with ondansetron was triphasic. At 10¯ψM it was 28.8%, whereas with 10¯ξM the amplitude decreased to 16.87%, it reached to plateau at 10¯Ï– M. Response of acetylcholine & serotonin was decreased to 57% and 78% respectively in the presence of fixed concentration of ondansetron (10¯Ï– M). Ondansetron reduces the acetylcholine and serotonin induced gastrointestinal motility. Our study has indicated that ondansetron apart from having central action also has marked peripheral actions that play an important role in CINV and may act as a partial agonist.

Comparative Study of Protective Effects of Salbutamol and Beclomethasone against Insulin Induced Airway Hyper-reactivity on Isolated Tracheal Smooth Muscle of Guinea Pig.

Inhalational insulin was withdrawn from the market due to its potential to produce airway hyper-reactivity and bronchoconstriction. So the present study was designed to explore the acute effects of insulin on airway reactivity of guinea pigs and protective effects of salbutamol and beclomethasone against insulin induced airway hyper-responsiveness on isolated tracheal smooth muscle of guinea pig. Effects of varying concentrations of insulin (10(-7) to 10(-3) M), insulin pretreated with fixed concentration of salbutamol (10(-7) M) and beclomethasone (10(-6) M) were studied on isolated tracheal tissue of guinea pig by constructing cumulative concentration response curves. Changes in tracheal smooth muscle contractions were recorded on four channel oscillograph. The mean ± SEM of maximum amplitudes of contraction with increasing concentrations of insulin, insulin pretreated with fixed concentration of salbutamol and beclomethasone were 35 ± 1.13 mm, 14.55 ± 0.62 mm and 22 ± 1.154 mm respectively. Although salbutamol and beclomethasone both had a profound inhibitory effect on insulin induced airway hyper-reactivity, yet salbutamol is more efficacious than beclomethasone. So we suggest that pretreatment of inhaled insulin with salbutamol may be preferred over beclomethasone in amelioration of its potential respiratory adverse effects such as bronchoconstriction.

Protective effect of metformin against gentamicin induced nephrotoxicity in rabbits.

Gentamicin is used against gram negative infections, but major problem encountered is nephrotoxicity that occurs in 10-20% of therapeutic regimes. Gentamicin induced oxidative stress plays an important role in this nephrotoxicity. Recent data has shown metformin to possess antioxidant activity. Purpose of study was to evaluate potential role of metformin in protecting kidney from nephrotoxicant insult. Thirty-six rabbits were randomly divided into six groups (n=6). G-1 received 1 ml isotonic saline intraperitoneally (IP) daily for 13 days. G-2 received gentamicin (150 mg/kg/day) IP for last 6 days of 13 days. G-3 received gentamicin (40 mg/kg/day) IP for 13 days. G-4 received metformin salt (100 mg/kg/day) dissolved in drinking water via feeding tube for 13 days. G-5 received metformin salt (100 mg/kg/day) via feeding tube for 13 days plus gentamicin (150mg/kg/day) IP for last 6 days of 13 days. G-6 received gentamicin (40mg/kg/day) IP plus metformin salt (100mg/kg/day) via feeding tube for 13 days. Blood was collected on days 0 and 14 for serum urea & creatinine estimation. All animals were sacrificed and kidneys were removed for renal histological examination. Metformin showed nephroprotective effect. It blunted nephrotoxic insult at 150mg/kg/day of gentamicin, whereas showed complete nephroprotection at 40mg/kg/day of gentamicin. Metformin offers complete nephroprotection at low toxic dose ranges of gentamicin. This could offer an efficacious and cheaper treatment alternative in those diabetics who also suffer from gram-negative infections.