EX-VIVO EFFECT OF INSULIN ON NORMAL AND DIABETIC RAT HEARTS HYPOPERFUSED WITH NOREPINEPHRINE

The effect of ex vivo insulin on contractile and energy metabolism dys functions was examined during hypoperfusion (0.6 ml/min per g heart we ight) with 10(-6) M norepinephrine in isolated non-diabetic and strept ozotocin-diabetic rats hearts. Insulin (2 mU/min per g heart weight) w as infused for 15 min before as well as during 60-min hypoperfusion. I nsulin significantly reduced the elevated diastolic tension in diabeti c hearts (from 3.8 to 0.7 DELTAg), but not in non-diabetic hearts (fro m 1.4 to 1.2 DELTAg). Insulin partly improved the ATP decrease in the subendocardium of the left ventricle of the diabetic hearts (from 3.5 to 10.2 mumol/g dry weight) but did not affect non-diabetic hearts (fr om 6.9 to 6.8 mumol/g dry weight). Insulin also partly improved the cr eatine phosphate decrease and the inorganic phosphate increase in diab etic hearts only. Lactate accumulation was greater in non-diabetic tha n in diabetic hearts, even in the presence of insulin (77 vs. 45 mumol /g dry weight). The results indicate that acute intracoronary applicat ion of insulin in diabetic hearts improves hypoperfusion with norepine phrine injury to a level above that of non-diabetic hearts, but does n ot improve a less severe injury in non-diabetic hearts.