Background: Impaired vasomotor function has been suggested as playing a role in the pathophysiology of atherosclerosis and it may also affect the late patency of bypass grafts. We evaluated, in vitro, the influence of risk factors of atherosclerosis on saphenous vein endothelial function in patients with cardiovascular diseases.
Methods: Forty-five saphenous vein rings with intact (E+) and denuded endothelium (E-) were studied. The following drugs were used: norepinephrine (NE), acetylcholine (Ach), histamine (H) and serotonine (5-HT).
Results: Contraction to norepinephrine (n=15) showed a maximal tension of 783+/-115 percent that was increased in diabetics, smokers, and patients with hypertension. There was a wide range of response to acetylcholine in rings with intact endothelium (n=25), (mean relaxation 16.4+/-1.7 percent, ranging from -22.2 percent to 45 percent) with relaxation (26+/-1.1 percent) and contraction (-11+/-1.2 percent); relaxation was reduced in patients with hypertension and in diabetics (7.4+/-2.6 percent vs non diabetics 24.4+/-1.73 percent; p<0.01). Five of the 12 veins from diabetics exibited contraction (10+/-1.48 percent). Histamine (n=15) caused moderate relaxation at low doses (25+/-2.46 percent) followed by contraction at higher concentrations (184+/-5.7 percent). This was greater in diabetics (193+/-6.8 percent vs non diabetics 157+/-5.3 percent; p=0.045) while in preparations without endothelium (n=10) only relaxation was obtained (45+/-2.89 percent). Contraction (242+/-7.4 percent) was observed in response to serotonine (n=15) that was not affected by endothelial removal. In this study saphenous vein: (1) exhibited a wide range of responses to acetylcholine; (2) evoked marked contraction to norepinephrine and serotonine; (3) elicited contraction in response to histamine that was endothelium-dependent, suggesting the production or the release of an endothelium-derived-contracting-factor (EDCF).
Conclusions: Saphenous vein is able to secrete a contracting factor in patients with risk factors of atherosclerosis and above all diabetes. The mechanisms that regulate the balance between the relaxing and contracting factors and how the endothelial cells become the source of the substances with vasoconstrictor activity remain to be determined.