RETENTION OF LEUKOCYTES IN REPERFUSED, ISOLATED HEARTS DOES NOT CAUSEHEMODYNAMICALLY RELEVANT PERMANENT CAPILLARY PLUGGING

Effects of microspheres (5 mu m or 10 mu m diameter) and polymorphonuc lear leucocytes (PMN) on coronary resistance were compared in beating, non-working isolated guinea-pig hearts (Langendorff preparation). The hearts were buffer perfused (5 ml/min, constant flow) and particles o r cells were infused into the coronary system as a bolus (1 mi, 1 min) . Coronary perfusion pressure, coronary flow and formation of epicardi al transudate were measured before and after bolus administration. Cor onary resistance was estimated from these parameters. Retention of par ticles or cells was monitored by quantifying the numbers emerging in t he coronary effluent in relation to the number administered. The effec ts of PMN were also studied after 15 min of global ischaemia. Coronary resistance correlated with the number of 10-mu m particles infused, w hich were almost quantitatively retained. In contrast, 5-mu m beads ha d no such effect and were not retained in the coronary system. Though considerable numbers of PMN were retained in the hearts (about 21% und er control conditions and 35% after ischaemia), coronary resistance wa s not increased in either case. Blockage of the CD18 adhesion complex by monoclonal antibodies lowered basal retention to 11% and completely prevented the elevation of retention by ischaemia. We conclude that, in this experimental model, PMN, permanently retained in the hearts un der normal now conditions and especially after brief ischaemia, do not cause acute, haemodynamically relevant capillary plugging, but adhere to postcapillary venules via CD18.