EFFECT OF EXPERIMENTAL NON-INSULIN REQUIRING DIABETES ON MYOCARDIAL MICROCIRCULATION DURING ISCHEMIA IN DOGS

To examine whether chronic high blood glucose may influence myocardial microcirculation during acute myocardial ischaemia in the dog, a noni nsulin-requiring diabetes was induced by the streptozotocin-alloxan me thod. Seventy-five days later, myocardial ischaemia was provoked by oc cluding the left anterior descending coronary artery for 2 h and micro circulation regulation was assessed in the ischaemic and non-ischaemic myocardium by the radioactive microsphere method. Diabetic dogs were compared with normal dogs. Diabetic dogs had higher blood glycated hae moglobin (2.66 +/- 0.4%) and fructosamine (397 +/- 62 mu mol l(-1)) th an control dogs (0.66 +/- 0.2, P < 0.004 and 229 +/- 13, P < 0.03, res pectively). Haemodynamic data in the two groups were not different at any time. The size of the ischaemic zone was similar in both groups. D uring the 2 h ischaemia in the ischaemic zone subendocardial (P = 0.22 ) and subepicardial (P < 0.05) blood flow slightly increased in contro l dogs whereas there was a 63% (P < 0.02) and 35% (P = 0.06) reduction respectively in diabetic dogs. In the non-ischaemic zone, blood flow of controls tended to increase (P < 0.006 in the subepicardium and P < 0.06 in the subendocardium) whereas in diabetic dogs blood flow tende d to decrease (P = 0.03 in the subendocardium and in the subepicardium ). This first investigation on myocardial microcirculation in diabetic dogs during ischaemia suggests that one of the possible causes of inc reased mortality rate from ischaemic cardiac disease in diabetics migh t be related to a paradoxical and unfavourable pattern of myocardial b lood flow during ischaemia.