The effect of rosiglitazone on the mechanic and electrical activity of papillary heart muscle in diabetic rats

It has been known that hyperglycemia and increased free fatty acids induce impairment of cardiac functions in diabetes mellitus. Diabetic cardiomyopathy which the major reason of mortality due to diabetes mellitus is a natural outcome in patients with long term expose to diabetes mellitus. The aim of this study was to investigate the possible mechanisms responsible for the mechanical and electrical alterations on left ventricular papillary muscle in a diabetic rat model.One hundred twenty Wistar albino male rats (Weighted, 270-300 gram) were used for the study. Streptozotocin (STZ: 45 mg/kg) solved in 0.1 M cold citrate buffer solution (pH=4.5) was given by route of tail vein and experimental diabetes mellitus induced in part of rats. The rats were divided into six groups; Controls (C), controls treated with RZG (C+RZG), diabetic rats (D), diabetic rats treated with RZG (D+RZG), diabetic rats treated with RZG and insulin (D+RZG+INS) and diabetic rats treated with insulin (D+INS). Four mg/kg/day RZG and 1 IU BID subcutaneous insulin (INS) were given in treatment groups.Significant reduction was observed in peak values of contractions at diabetic process (p<0,05). It has been shown that the reason of significant prolongation of contraction period was prolongation of release and reuptake of Ca+2. In addition, contraction parameters of treatment groups were approached to those of C group.It was concluded that the reason of significant prolongation of action potential recorded with classical microelectrode recording technique in diabetic rats was reduction of density of potassium channel.Treatment with RZG was improved some parameters (weight, blood glucose level vs.) in experimental induced diabetic rats. The study was also shown that in vivo treatments were caused to improvement in durations of action potential and contraction.Increase in hemoglobin A1C, homocysteine, total cholesterol, HDL and LDL cholesterol and triglyceride values with diabetic process and reduction in those values with treatment were observed.In conclusion, variations in induction-contraction coupling after experimental induction of diabetes mellitus by STZ are observed. Those variations are approached to control values by using rosiglitazone.KEYWORDS: Diabetes, Rat papillary heart muscle, Rosiglitazone, Contraction, Action potential, Membrane potential.