RESUMO
INTRODUCTION: In order to evaluate endothelial response to platelet single passage through coronary vascular bed, experiments on isolated guinea-pig hearts perfused by the Langendorff method at constant pressure were performed. MATERIAL AND METHODS: Platelet single passage was performed with platelet-rich plasma obtained from healthy volunteers, as well as from patients with acute myocardial infarction. Hearts, isolated from guinea-pigs of either sex were perfused with Krebs-Hensenleit buffer. After a stabilization period of 30 minutes at 70 cm H2O, coronary perfusion pressure decreased to 30 cm H2O and increased to 120 cm H2O. After basic protocol, hearts were perfused with PRP, PRP-AMI alone or in combination with nitric oxide synthase inhibitor, N(omega)-nitro-L arginine methyl ester (L-NAME)--30 M, and nitrite outflow (NO2-) was measured. RESULTS: Basal (at 70 cm H2O) coronary flow (CF) and NO2- was 4.71+/-0.43 ml/min and 0.55+/-0.13 nmol/min/g wt. PRP induced significant decrease of CF at all values of CPP (from 32% at 30 cm H2O to 27% at 120 cm H2O), with parallel NO2- reduction (from 25% to 28%). When L-NAME, 30 M was added, PRP was much less effective: CF was reduced from 13% to 5%, with parallel changes of NO2- (reduction of 10% at all CPP values). PRP-AMI induced higher degree of CF reduction (from 42% to 44%) with NO2 reduction from 23% to 35%. PRP-AMI after applied L-NAME induced also less CF-reduction (from 18% to 12%), with similar NO2- reduction (from 18% to 12%). CONCLUSION: Our findings show that effects of platelet single passage through coronary vascular bed should be affected by NO in isolated guinea-pig hearts.
