Mental stress opposes endothelium-dependent vasodilation in young healthy individuals

Mental stress has been shown to induce myocardial ischemia in people with coronary heart disease (CHD), both in the laboratory and in daily life. In order to investigate the role of the endothelium in the regulation of blood flow during stress, the endothelium-dependent (EDV) and endothelium-independent (EIDV) vasodilation was examined in the forearms of healthy people during a mental arithmetic test (MAT), a cold pressor test (CP) and an isometric handgrip test (ISO). A total of 10 young healthy volunteers (four men and six women, aged 20-25 years) underwent measurements of forearm vascular resistance (FVR) during local intraarterial infusions of methacholine (MCh; inducing EDV) and sodium nitroprusside (SNP; inducing EIDV) at rest and during the different forms of stress by the use of venous occlusion plethysmography. MAT induced a significant increase in FVR during MCh infusion (4 microg/min, from 3.5 +/- 0.7 at rest to 4.2 +/- 1.4 mmHg/ml per min per 100 ml tissue during MAT; p < 0.01), while FVR during SNP infusion was unchanged by MAT. CP induced a significant increase in FVR during infusions with both MCh and SNP compared to resting levels (p < 0.01 for both), while ISO induced a significant increase in FVR during MCh infusion (p < 0.05) and a smaller increase in FVR during SNP infusion. When the SNP to MCh FVR ratio was used as an index of endothelial function, only MAT impaired endothelial function significantly (p < 0.01). In conclusion, mental stress induced by an arithmetic task selectively opposed EDV in the forearms of young healthy people, while cold pressor and isometric handgrip tests induced a more general attenuation in vasodilatation.