The effect of L-carnitine on nitric oxide metabolism in streptozotocin-induced diabetic rats

Objective: The aim of this study is to investigate the effect of L-carnitine on plasma and liver nitric oxide metabolism in streptozotocin-induced diabetic rats. Methods: Sprague Dawley female rats were divided randomly into following groups: control, Lcarnitine, diabetes and diabetes+L-carnitine. Diabetes and diabetes+L-carnitine groups were intraperitonally injected with a single dose of streptozotocin (40 mg/kg) prepared in the citrate buffer (pH 4.5). Other groups were injected with only citrate buffer. 72 hours after the streptozotocin injection, Lcarnitine (500 mg/kg/day) was given intraperitoneally to L-carnitine and diabetes+L-carnitine groups for 15 days. Physiological saline was given intraperitoneally to the other groups for 15 days. Blood sugar (at 72 hours and the end of experiment), liver nitric oxide and inducible nitric oxide synthase, plasma nitric oxide and nitrotyrosine levels were measured. Results: Blood glucose levels in diabetic groups were higher compared with other groups. Percentage change of blood glucose in diabetes+L-carnitine group was lower compared with other groups. Also diabetes+L-carnitine group’s plasma nitric oxide levels were higher than control group. Plasma nitrotyrosine levels of L-carnitine injected groups were lower than diabetes group. There was no significant difference between the levels of liver inducible nitric oxide synthase and nitric oxide in groups. Conclusion: As a result, our study showed that plasma and liver nitric oxide and liver inducible nitric oxide synthase levels aren’t changed significantly but plasma nitrotyrosine levels are increased at the end of 15th day of experimental diabetes. On the other hand, our results also showed that L-carnitine causes an increase in plasma nitric oxide levels and a decrease in plasma nitrotyrosine levels whereas it has no effect on liver nitric oxide and inducible nitric oxide synthase levels.