The analysis of ultrastructure and gene expression of sarco/endoplasmic reticulum calcium handling proteins in alloxan-induced diabetic rat myocardium.

摘要

OBJECTIVE: The change of mechanical properties of isolated diabetic rat papillary muscle, myocardial ultrastructure and gene expression of sarco/endoplasic reticulum calcium handling proteins in alloxan-induced diabetic rat heart was investigated. METHODS: Diabetes was induced in male Sprague-Dawley rats (180-220 g) by administering a single tail-vein injection (40 mg/kg) of alloxan. The control group was injected with normal saline. At the end of 2, 4 and 6 weeks after the induction of diabetes, the right ventricular papillary muscles were isolated and perfused with oxygen saturated Tyrode solution for assessment of the contractile function. Light and electron microscopic analysis was used to analyse the myocardial ultrastructure in rats six weeks after induction. Gene expression of calcium handling proteins was measured by reverse transcription-polymerase chain reaction and Western blot. RESULTS: In the diabetic rats, +dT/dtmax and -dT/dtmax were decreased (P < 0.01), while 1/2 diastolic intervals were longer than control at the end of 4 and 6 weeks (P < 0.01). Electron microscopic analysis of the myocardium revealed a spectrum of subcellular remodelling which was characterized by damaged myofibrils and mitochondria and dilated swollen sarcoplasmic reticulum. The levels of both mRNA and protein of phospholamban were significantly increased, whereas 1, 4, 5-trisphophate inositol receptor type 2, ryanodine receptor type 2 mRNAs were significantly decreased compared with that in the age-matched 6 weeks control rats. In contrast, levels of both mRNA and protein of sarco/endoplasic reticulum Ca2+ -ATPase were not affected. CONCLUSIONS: Contractile dysfunction of papillary muscles and subcellular remodelling exist in alloxan-induced diabetic rat myocardium. Up-regulation of phospholamban and down-regulation of sarco/endoplasic reticulum calcium release channel may be the molecular mechanism.