Blood pressure-related changes of endothelium-dependent relaxation in the aorta from SHRSP at developmental ages of hypertension.

1. Shear stress and flow influence endothelial functions to stimulate the release of endothelium-derived relaxing factor (EDRF). However, it is not well defined how hypertension affects endothelial functions. In this study, blood pressure-related changes of endothelium-dependent relaxation (EDR) in the aorta were examined in SHRSP, WKY and F1 hybrid at developmental ages of hypertension, and hypotensively-treated SHRSP. 2. Acetylcholine-induced EDR of aortic rings was significantly enhanced in 8 week old SHRSP compared with that of age-matched WKY. 3. NG-monomethyl L-arginine (L-NMMA) (1 mmol/L), an inhibitor of nitric oxide, greatly reduced the relaxation in both strains. Indomethacin (10(-5) mol/L), a cyclo-oxygenase inhibitor, did not affect the relaxation at this age. 4. EDR was positively correlated (r = 0.81, n = 22) with blood pressure at 9 weeks of age in WKY, SHRSP and F1 hybrid. 5. A five week hypotensive treatment of SHRSP caused a significant reduction in EDR with decreasing blood pressure. 6. It was concluded that the endothelium releases more EDRF in response to increasing blood pressure to regulate vascular tone at developmental ages of hypertension.