OBJECTIVETo investigate the ultrastructure of myocardium and gene expression of calcium handling proteins in diabetic rat heart.

METHODSDiabetes was induced in male Sprague-Dawley rats by a single injection of alloxanm (40 mg/kg ) and the rats in control group were injected with normal saline. At the end of 2, 4, 6 weeks after the induction of diabetes, the animals were sacrificed. The expression of calcium handling proteins was detected by reverse transcription-polymerase chain reaction (RT-PCR) and actin mRNA was used as internal standard. Heart tissue at the apex was obtained for light and electron microscope study.

RESULTSAt the end of 4 and 6 weeks, cardiosomatic ratio of diabetic rats was higher than that of control. Electron microscopy revealed a spectrum of subcellular remodeling in myocardium which was characterized by damaged myofibrils and mitochondria, dilated and swollen sarcoplasmic reticulum. Expression of phospholamban mRNAs was significantly increased, but 1,4,5-trisphosphate inositol receptor type 2, ryanodine receptor type 2 mRNAs were significantly decreased compared with those in the age-matched control rats. In contrast, the expression of sarco/endoplasmic reticulum Ca(2+)-ATPase mRNAs was not affected.

CONCLUSIONIn diabetic rat heart, gene expression of calcium handling proteins was characterized by up-regulation of phospholamban and down-regulation of sarcoplasmic reticulum calcium release channel while electron microscopic analysis of myocardium revealed a spectrum of subcellular remodeling.