ISCHEMIC EPISODES OF LESS-THAN 5 MINUTES PRODUCE PRECONDITIONING BUT NOT STUNNING IN THE ISOLATED RAT-HEART

The aim of the present study was to examine whether ischaemic episodes of less than 5 min could induce preconditioning or stunning in the is olated rat heart. Hearts were subjected to total global ischaemia of 1 , 2 and 4 min followed by 10 min of reperfusion before an 18-min main ischaemic period and 30 min of reperfusion. The effects on physiology, purine metabolism and anaerobic glycolysis were compared with a contr ol group subjected to the main ischaemia only. The brief ischaemic epi sodes did not produce stunning based on the recovery of left ventricul ar developed pressure (LVDP) and heart rate (HR) product during the fi rst reperfusion. Preconditioning of 11-14% increased recovery of LVDP x HR during the second reperfusion was observed in the 1- and 4-min gr oup. In the 2-min group a low repayment of flow debt during the first reperfusion was associated with a slightly reduced recovery of LVDP x HR compared to the other preconditioned groups during the second reper fusion. Only in the 4-min group was preconditioning associated with fe wer breakdown products of the purine nucleotide pool (adenosine) and a naerobic glycolysis (lactate) in both tissue and efflaute after the ma in ischaemia. Preconditioning (reflected in recovery of function) coul d be produced with ischaemic episodes of less than 5 min that did not produce stunning. Thus, stunning is probably not the primary cause of preconditioning.