Effects of noise on blood pressure and vascular reactivities.

1. The present study investigated the effects of noise stress (100 dB, 1 kHz, 4 h/day, 6 days/week) on both systolic blood pressure and vascular reactivities in rats exposed to noise for 2 and 4 weeks. The systolic blood pressure was significantly increased after rats were exposed to noise for 4 weeks but not 2 weeks. 2. In isolated thoracic aortic rings, the responses to serotonin were enhanced in noise-treated rats while there were no changes in response to phenylephrine and high K+ between noise-treated and control rats. 3. The relaxant responses to endothelium-dependent vasodilators (A23187 and acetylcholine) in noise-treated rats were less than those in control rats. The vasodilator responses to acetylcholine were completely abolished by methylene blue or N omega-nitro-L-arginine. 4. Responses to the endothelium-independent vasodilator, nitroglycerin, were not significantly changed after rats were exposed to noise. 5. The enhanced response to vasoconstrictors and the attenuation to endothelium-dependent vasodilators may account for elevations in blood pressure during noise stress. This indicates that the elevation in blood pressure by noise stress may be partly due to the deterioration of endothelial function.