THE REVERSIBILITY OF IMPAIRED PROSTACYCLIN PRODUCTION OF THE VEIN GRAFT

The effects of changes in shear stress (shear stress variation) on production of prostacyclin (PGI2) were examined in canine autologous vein grafts, which were implanted in the poor or normal distal runoff limbs. Four weeks after grafting, the vein grafts were perfused ex vivo and PGI2 was assayed as 6-ketoprostaglandin F(1α). The vein grafts were perfused under constant flow for the first 30 min and then under pulsatile flow simulating an abnormal flow with a low shear stress variation or a normal flow with a high shear stress variation for the next 30 min. Basal production rates (30- min cumulative PGI2 production) of vein grafts implanted in the poor runoff and normal runoff limbs were 1.97 ± 0.71 and 2.19 ± 0.40 ng/cm2, respectively, with no significant difference. Pulsatile flow effects (increased PGI2 production between 30 and 60 min) of simulated abnormal versus normal flow were 0.50 ± 0.50 ng/cm2 versus 2.31 ± 1.87 ng/cm2 in vein grafts implanted in poor runoff limbs (P < 0.05) and 0.48 ± 0.41 ng/cm2 versus 3.48 ± 1.08 ng/cm2 in vein grafts implanted in normal runoff limbs (P < 0.01), respectively. There were no significant differences in simulated normal flow effects between poor runoff limbs and normal runoff limbs. The results indicate that the release of PGI2 in vein grafts may decrease in the presence of an abnormal blood flow with a low shear stress variation. In addition, it is suggested that even vein grafts implanted in the poor runoff could increase PGI2 production once the grafts were placed into normal arterial circulation. © 1993 Academic Press, Inc.