AGE-RELATED DIFFERENCES IN RESPONSE TO NEUTROPHIL-MEDIATED REPERFUSION INJURY IN THE NEONATAL PIGLET HEART

Background. Neonatal hearts have altered adhesion molecule interaction s in response to ischemia-reperfusion. How this affects myocardial fun ction is unknown. Methods, isolated Buffer perfused 0- to 2-day (newbo rn) and 2-week piglet hearts were first subjected to 20-minute global, normothermic ischemia, followed by 45 minutes of reperfusion during w hich 150 x 10(6) newborn or 2-week neutrophils were infused. In some h earts, an antibody to SLe(x) (CSLEX-1) was infused with neutrophils du ring reperfusion. Hemodynamic variables, including left ventricular de veloped pressure (LVDP), were recorded at timed intervals. Neutrophil CD-18, L-selectin, and SLe(x) contents were measured by flow cytometry . Results, Full recovery of LVDP was observed in newborn hearts receiv ing newborn or 2-week-old neutrophils. Recovery of LVDP was depressed (P < 0.01, ANOVA) in 2-week-old hearts receiving 2-week old, not newbo rn, neutrophils. Infusion of CSLEX-1 in 2-week-old hearts restored LVD P to baseline. Whereas flow cytometry showed higher (p < 0.01, Student 's t test) CD-18 and L-selectin expression on newborn versus 2-week-ol d neutrophils, newborn neutrophils expressed lower (p < 0.01) SLe(x) I m,els. Conclusions. Initial ''loose'' neutrophil-endothelial selectin interactions are a necessary prelude to ''firm'' adhesion and reperfus ion injury. Operations performed soon after birth may be better tolera ted than when surgery is delayed; anti-SLe(x) preparations may prove b eneficial when performing cardiac procedures on older infants.