ATRIAL NATRIURETIC PEPTIDE-INDUCED RELEASE OF CYCLIC GUANOSINE-MONOPHOSPHATE BY CORONARY-BYPASS GRAFTS

Background. Superior long-term patency rates of the internal mammary a rtery (IMA) versus saphenous vein (SV) after coronary artery bypass gr afting are well documented. Higher production rates of vasodilating an d platelet-inhibiting mediators (prostacyclin and nitric oxide) by the IMA seem to have a major impact on its long-term durability and resis tance to coronary artery graft disease. For the right gastroepiploic a rtery (RGEA) marked release of protective mediators is reported as wel l. The vasodilating effect of cyclic guanosine monophosphate (cGMP) re leased after stimulation by atrial natriuretic peptide might serve as another graft protective system. The aim of the present study was to d etermine cGMP release by IMA, RGEA, and SV after atrial natriuretic pe ptide challenge. Methods. Samples of human IMA (n = 19), RGEA (n = 7), and SV (n = 18) discarded during coronary artery bypass grafting were stimulated with 10(-6) mol/L atrial natriuretic peptide after a resti ng phase in nutrient medium. Release of cGMP was determined by 125-iod ide radioimmunoassay. Results. Basal cGMP production rates of the IMA (759.9 +/- 277.0 fmol/cm(2)) and RGEA (739.9 +/- 186.0 fmol/cm(2)) wer e higher than production rates of SV (281.2 +/- 64.0 fmol/cm(2)). Appl ication of atrial natriuretic peptide led to a statistically significa nt increase of cGMP release in IMA grafts (1,939.3 +/- 778.0 fmol/cm(2 )), whereas RGEA (618.4 +/- 141.3 fmol/cm(2)) and SV (221.7 +/- 64.5 f mol/cm(2)) remained at basal levels (p < 0.05). Conclusions. From thes e data we conclude that the IMA in comparison with the RGEA and SV pro duces more extracellular cGMP when stimulated by atrial natriuretic pe ptide. This effect might support the cGMP-mediated protective properti es of nitric oxide and could underline the extraordinary suitability o f the IMA as a bypass conduit. (C) 1998 by The Society of Thoracic Sur geons.