Tanaka Y, Konno N, Kako K J
Department of Physiology, Faculty of Medicine, University of Ottawa, Ontario, Canada.
Cardiovasc Res. 1992 Apr;26(4):409-14. doi: 10.1093/cvr/26.4.409.
The aim was to investigate effects of experimental diabetes and insulin treatment on heart myocytes, particularly on the mitochondrial function studied in situ in isolated cardiomyocytes.
20 male Sprague-Dawley rats (140-160 g) were made diabetic by intraperitoneal streptozotocin, 70 mg.kg-1. Ten then received daily subcutaneous injections of ultra lente insulin (starting dose of 3 units.d-1) for 7-15 d from the 20th day after streptozotocin. There was a control group of 11 rats. The rats were killed 21-35 d after the induction of diabetes, and heart myocytes were isolated by collagenase digestion. The 45[Ca]2+ uptake of mitochondria in situ in permeabilised myocytes, the transmembrane potential gradient of mitochondria, and the respiration of myocytes, as well as the cell yield and cell [45Ca]2+ uptake, were examined.
Mitochondrial uptake of [45Ca]2+ was significantly decreased in the diabetic group compared to control at cytosolic calcium concentrations between 760 nM and 44.6 microM. The mitochondrial potential of diabetic myocytes, estimated from the distribution of [3H]triphenylmethylphosphonium+, was slightly but significantly decreased from the control value. Cell respiration, measured polarographically in the presence of pyruvate and malate or succinate as oxidisable substrates, and with or without 2,4-dinitrophenol, was decreased by diabetes. The rapidly exchangeable [45Ca]2+ content in the myocyte with intact sarcolemmal membrane ("cell Ca2+ uptake") and the yield of cells from heart tissue were also diminished in diabetic rats. These changes were returned to normal by insulin treatment of 7 d or longer.
Insulin deficiency at early stages causes defects of mitochondrial function detectable in situ in cardiomyocytes. This suggests the possibility that such alterations are causative factors in the development of diabetic cardiomyopathy.
研究实验性糖尿病及胰岛素治疗对心肌细胞的影响，特别是对分离的心肌细胞原位线粒体功能的影响。
20只雄性Sprague-Dawley大鼠（体重140 - 160克）腹腔注射70毫克/千克链脲佐菌素制成糖尿病模型。其中10只从注射链脲佐菌素后第20天起每天皮下注射超长效胰岛素（起始剂量为3单位/天），持续7 - 15天。另有11只大鼠作为对照组。在诱导糖尿病后21 - 35天处死大鼠，通过胶原酶消化分离心肌细胞。检测通透化心肌细胞中线粒体对45[Ca]2+的摄取、线粒体跨膜电位梯度、心肌细胞呼吸，以及细胞产量和细胞对[45Ca]2+的摄取。
在细胞溶质钙浓度为760纳摩尔至44.6微摩尔之间时，与对照组相比，糖尿病组线粒体对[45Ca]2+的摄取显著降低。根据[3H]三苯基甲基鏻离子的分布估算，糖尿病心肌细胞的线粒体电位较对照值略有但显著降低。以丙酮酸和苹果酸或琥珀酸作为可氧化底物，通过极谱法测量细胞呼吸，无论有无2,4 - 二硝基苯酚，糖尿病均使其降低。糖尿病大鼠中，具有完整肌膜的心肌细胞中快速可交换的[45Ca]2+含量（“细胞Ca2+摄取”）以及心脏组织中的细胞产量也降低。胰岛素治疗7天或更长时间可使这些变化恢复正常。
早期胰岛素缺乏会导致心肌细胞原位可检测到的线粒体功能缺陷。这提示这种改变可能是糖尿病心肌病发生发展的致病因素。
