Original article: PDF OnlyDifferential effects of vasopressin and endothelin-1 on vascular contractile and calcium responses in pressurized small arteries from spontaneously hypertensive ratsTouyz, Rhian M.; Deng, Li-Yuan; Li, Jin-Sheng; Schiffrin, Ernesto L.Author Information MRC Multidisciplinary Research Group on Hypertension, Clinical Research Institute of Montréal, University of Montréal, Montréal, Québec, Canada. Journal of Hypertension: August 1996 - Volume 14 - Issue 8 - p 983-992 Buy Abstract Objective To investigate the effects of vasopressin and endothelin-1 on the intracellular free calcium concentration ([Ca2+]i) and on contractile responses in endothelium-denuded resistance vessels of prehypertensive (5-week-old) and adult hypertensive (17-week-old) spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto (WKY) rats. Methods Segments (2 mm long) of third-order branches of small mesenteric arteries were mounted in a perfusion myograph and maintained at 60mmHg pressure. Endothelium was removed by intraluminal passage of air. The vessel [Ca2+]i was measured by fura-2 fluorescence and contraction was determined using a video imaging system to record lumen diameter. Results Lumen diameter was significantly smaller in 5-and 17-week-old SHR than it was in age-matched WKY rats (5 week-old SHR versus WKY rats: 178 ± 4.0 versus 195 ± 4.3 μm; 17-week-old SHR versus WKY rats: 168 ± 7.0 versus 230 ± 3.1 μm). The basal [Ca2+]i was significantly higher in 5− and 17-week-old SHR than it was in age-matched WKY rats. Infusions of vasopressin and endothelin-1 increased [Ca2+]i and contractile responses in a dose-dependent manner in all groups. The vasopressin-induced change in [Ca2+]i was significantly greater in 5− and 17-week-old SHR than in age-matched controls. The sensitivity of [Ca2+]i to vasopressin was increased in adult SHR compared with WKY rats (pD2 9.0 ± 0.1 in SHR, 8.2 ± 0.3 in WKY rats). Vasopressin-stimulated contractile responses were increased in adult SHR. The endothelin-1-induced change in [Ca2+]i did not differ between WKY rats and SHR. The contractility of vessels in response to endothelin-1 infusion was similar in age-matched groups. Conclusions Endothelin-1-induced changes in [Ca2+]i and contractile responses in small arteries are similar in age-matched WKY rats and SHR, whereas responses to vasopressin are significantly enhanced in SHR compared with WKY rats. Thus [Ca2+]j signalling for vasopressin is more active than is that for endothelin-1. Vasopressin but not endothelin-1 might play a role in the development of hypertension in SHR. © Lippincott-Raven Publishers.