Effects of Endothelin-A Receptor Antagonist BQ-123 on Plasma Leptin Levels in Streptozotocin-induced Diabetic Rats

Objective: Leptin and endothelin (ET) as important endogenous factors interacting with each other which may contribute to a better understanding of their role in diabetic pathogenesis. We aimed to evaluate the relationship between leptin and ET by investigating the influence of BQ-123, an ET-A receptor (ET AR) antagonist, on leptin levels in rats with diabetes induced by streptozotocin (STZ). Methods: In this study, 24 male Wistar albino rats were divided into three groups: control, STZ and STZ+BQ-123 groups. Experimental diabetes was induced by delivering a single dose of 60 mg/kg intravenous STZ. The rats in the STZ+BQ-123 group received 4 mg/kg i.v. in total BQ-123 (2 mg/kg +2 mg/kg on the 39th and 40th days). The plasma specimens collected 6 hours after the last BQ-123 delivery were studied for biochemical parameters. Results: At the end of the experiment, the weights of rats in the STZ and STZ+BQ-123 groups were significantly lower compared with the values in the control group. The levels of blood glucose were significantly higher in the STZ and STZ+BQ-123 groups than in the control group. While rats with STZ-induced diabetes demonstrated no changes in leptin, protein carbonyl and K+ levels, they exhibited reduced NO, Na+ and Cl- concentrations. The levels of plasma thiobarbituric acid-reactive substance were significantly higher in the STZ group than in the control and STZ+BQ-123 groups. Conclusion: Although the levels of plasma leptin were not statistically significant different between the groups, BQ-123 groups lead to a further decrease in reduced levels of leptin than in only diabetic group. Our findings have been considered that ET AR antagonists have positive impacts depending on the dosage in the diabetic rats.