Comparison of functional responses of canine coronary artery and saphenous vein.

Functional responses of canine circumflex coronary arteries and saphenous veins before and after grafting surgery were assessed following physiologic and pharmacologic interventions. Developed tension of ringed segments of vessels was recorded isometrically. Dose-dependent responses to norepinephrine revealed significantly greater responses of saphenous veins than coronary arteries (maximal responses were 2.79 +/- 0.45 and 0.44 +/- 0.34 g, respectively; p less than 0.001). Sensitivity to norepinephrine [as evaluated by 50% effective dose (ED50) value] was 3.3 times greater in the saphenous veins (p less than 0.001). STA2, a synthetic thromboxane A2 analog (see Methods), produced similar contractions of both vessels [maximal responses were 2.13 +/- 0.37 g in saphenous vein and 1.64 +/- 0.85 g in coronary artery; p less than not significant (NS)], while sensitivity to STA2 of saphenous veins was 3.1 times greater than that of coronary arteries (p less than 0.001). In contrast to the foregoing responses, coronary arteries demonstrated significantly greater responses to potassium than saphenous veins (maximal responses were 2.16 +/- 0.71 g and 1.40 +/- 0.56 g, respectively; p less than 0.001). Moreover, coronary arteries revealed 1.6 times greater sensitivity than saphenous veins (p less than 0.001). When saphenous veins were transplanted into the femoral artery, the segments of the grafts (2 weeks or 3 months after surgery) revealed 4.0 and 1.7 times greater sensitivity (denervation supersensitivity) to norepinephrine and potassium than those of the control veins (p less than 0.01, respectively). Contractile tension response, however, decreased by at least 50% 3 months after surgery, most probably due to a thickened vessel wall and a reduced compliance.(ABSTRACT TRUNCATED AT 250 WORDS)