Effects of insulin on diabetic mammalian cardiac muscle

40 EFFECTS OF INSULIN ON DIABETIC MAMMALIAN CARDIAC MUSCLE. I. Imanaga, R. Kamei, M. Kuroiwa, A. Uehara. Dept. of Physiol., School of Med., Fukuoka Univ., Fukuoka, Japan Effects of insulin(0.5U/ml) on t;an$membrane potential, contractility and sarcolemmal Na -K ATPase activity were examined in the right ventricular papillary muscle isolated from diabetic dog heart(DPM) induced by streptozotocin, and these results were compared with those in the preparation from non-diabetic dog(control).Resting membrane potential(RP) and hyperpolarization induced by insulin were less TegTtive and lesser in the DPM than those in the control.Na -K ATPase activity and its rise by insulin were remarkably lower(46.3% in average) and weaker in the DPM than those in the control.Positive inotropic effect of insulin on the DPM was lesser(145.5&4%) than that on the contro1(209,6+9%).Recovery of the deteriorated contractility and RP by insulin under hypoxia was almost complete in the control, while it was fairly depressed in the DPM. These results suggest that Na-pump activity of the membrane, permeability of K+ ion to the membrane and glucose utilization of the cell, and their responses to insulin are impaired in the diabetic cardiac muscle.

CHANGES IN CONRACTILE PROTEINS OF ALLOXAN DIABETIC RAT HEARTS. H.Maeno. M.Shiozaki. T.Shikano. M.Nagano. Depertment of Internal Medicine,School of Medicine,Jikei University,Tokyo,Japan. Previously we showed that contractile proteins of human diabetic hearts had significant changes in the proportion of actomyosin. Current study was aimed to reveal 1) the proportion of actomyosin subunits 2) &activated ATPase activities and the superprecipitation of actomyosin from hearts of alloxan diabetic rats. This study was performed 7 weeks after i.v. injection of alloxan(5Omg/kg). The results indicated a significant increase in the proportion of the heavy chain to the myosin subunits from hearts of alloxan diabetic rats. The &activated ATPase activity was a significant decrement in the actomyosin from these subjects.The rate of the superprecipitation was decreased in the actomyosin from hearts of alloxan diabetic rats compared with normal.