The aim of this study was to assess whether
cyclooxygenase (COX) inhibitors protect the endothelial function against the deleterious effect of
ischemia and reperfusion. Isolated rat hearts perfused under constant-flow conditions were exposed to 30 min of partial
ischemia (flow, 1 ml/min) followed by 20 min of reperfusion, after which coronaries were precontracted with
U-46619, and the response to the endothelium-dependent
vasodilator,
serotonin (5-HT), was compared with that of the endothelium-independent
vasodilator,
sodium nitroprusside (SNP). In untreated hearts,
ischemia diminished selectively 5-HT-induced vasodilation, compared with
sham hearts (without
ischemia). The vasodilation to SNP was unaffected in all groups. Pretreatment with 6-MNA, 30 microM, a
COX-2 inhibitor with some activity on COX 1,
diclofenac, 1 microM (COX-1 and -2), or 1-(7-carboxyheptyl)
imidazole, 10 microM [
thromboxane (TX) synthase inhibitor] but not
indomethacin, 10 microM (COX-1 inhibitor) preserved the vasodilation induced by
5-HT after
ischemia.
Enzyme immunoassays indicated that all COX inhibitors decreased the concentration of TXB2 and 6-keto-PGF1alpha [stable metabolites of TXA2 and
prostacyclin (PGI2), respectively] in coronary effluent during
ischemia. Furthermore,
indomethacin was the only one to abolish the concentration of
PGE2 during
ischemia and early reperfusion. No clear trend on ventricular postischemic recovery could be observed between treated and untreated groups under our experimental protocols. These data suggest that, under our conditions, 6-MNA,
diclofenac, and 1-7-CHI, but not
indomethacin, protect the endothelial function via a reduction in TX concentration. Disparities between COX inhibitors may be due to the complete abolition of
PGE2 concentration during
ischemia and reperfusion in the
indomethacin group.