Leucocyte depletion attenuates the early increase in myocardial capillary permeability to small hydrophilic solutes following ischaemia and reperfusion

OBJECTIVE: The aim was to assess the significance of polymorphonuclear leucocytes on the myocardial capillary permeability to a small hydrophilic indicator, on the vascular tone of the resistance vessels, and on contractile function following ischaemia and reperfusion.

METHODS: Open chest, anaesthetised dogs were randomised to treatment with polyclonal antibody against polymorphonuclear leucocytes (anti-PMN group) or non-specific antibody (control group), and subjected to 40 min of coronary occlusion followed by 3 h of reperfusion. The capillary extraction fraction and the myocardial plasma flow rate were quantitated in vivo by intracoronary indicator bolus injection and external registration of the washout, and the capillary permeability-surface area product was calculated. Postischaemic vasodilator tone in the myocardial resistance vessels was measured by the local 133xenon washout method.

RESULTS: 20 dogs were included (10 in each group), and 13 dogs completed the ischaemia-reperfusion protocol (anti-PMN group, n = 7; control group, n = 6). In the anti-PMN group, blood polymorphonuclear leucocyte counts were reduced to a minimum of 15% of pretreatment values. After ischaemia and 5 min reperfusion, the capillary extraction increased by 17% in the control group but decreased by 22% in the anti-PMN group (p < 0.05). The corresponding capillary permeability-surface area product increased by 22% in the control group, but decreased by 16% in the anti-PMN group (p < 0.05). Neither maximum myocardial plasma flow during reactive hyperaemia nor contractile function were influenced by anti-PMN treatment.

CONCLUSIONS: Polymorphonuclear leucocytes appear to participate in the increase in myocardial capillary permeability observed early after reperfusion following a 40 min period of ischaemia, but do not influence postischaemic vascular tone or postischaemic contractile function. During normal physiological conditions reduction of the circulating polymorphonuclear leucocyte counts did not induce significant changes in myocardial capillary permeability.