Shigehiro Hayashi1, R Kelly Hester. 1. Department of Medical Pharmacology and Toxicology, and Microcirculation Research Institute, College of Medicine, Texas A&M University, College Station, TX 77843-1114, USA. s-hayashi@pha.ohu-u.ac.jp
Abstract
AIM: To quantitatively assess the effect of lowering external Ca(2+) ([Ca(2+)](o)) on both endothelium-dependent and -independent relaxations in rabbit aorta. METHODS: Isometric contractions and relaxations of isolated aortae were recorded. When assessing the effect of reduced [Ca(2+)](o) on relaxations, the normal [Ca(2+)](o) solution was substituted with one of the reduced [Ca(2+)](o) solutions for one aorta, while a paired aorta was replenished with normal [Ca(2+)](o) solution. RESULTS: The extent of acetylcholine (ACh)-induced relaxation, which is dependent on an intact endothelium, is time-dependent, and inversely related to [Ca(2+)](o) in a range of 0.02-2 mmol/L. ACh-induced relaxations were not significantly altered by the magnitude of the precontraction induced by PGF(2alpha). Nitroprusside-induced relaxations, which are independent of the endothelium, are also attenuated by reduced [Ca(2+)](o). Relaxant responses to ACh were significantly more susceptible to reduced [Ca(2+)](o) than nitroprusside-induced relaxations. A maximally effective relaxing concentration of D600, an L-type Ca channel blocker methoxyverapamil, (10(-5) mol/L) attenuated ACh-induced relaxations, whereas nitroprusside-induced relaxations were unaffected by D600. CONCLUSION: Thus, endothelium-dependent relaxation is more dependent on [Ca(2+)](o) than endothelium-independent relaxation, and it seems likely that [Ca(2+)](o) plays an important role not only in contractile processes, but also in relaxant processes as well.
AIM: To quantitatively assess the effect of lowering external Ca(2+) ([Ca(2+)](o)) on both endothelium-dependent and -independent relaxations in rabbit aorta. METHODS: Isometric contractions and relaxations of isolated aortae were recorded. When assessing the effect of reduced [Ca(2+)](o) on relaxations, the normal [Ca(2+)](o) solution was substituted with one of the reduced [Ca(2+)](o) solutions for one aorta, while a paired aorta was replenished with normal [Ca(2+)](o) solution. RESULTS: The extent of acetylcholine (ACh)-induced relaxation, which is dependent on an intact endothelium, is time-dependent, and inversely related to [Ca(2+)](o) in a range of 0.02-2 mmol/L. ACh-induced relaxations were not significantly altered by the magnitude of the precontraction induced by PGF(2alpha). Nitroprusside-induced relaxations, which are independent of the endothelium, are also attenuated by reduced [Ca(2+)](o). Relaxant responses to ACh were significantly more susceptible to reduced [Ca(2+)](o) than nitroprusside-induced relaxations. A maximally effective relaxing concentration of D600, an L-type Ca channel blocker methoxyverapamil, (10(-5) mol/L) attenuated ACh-induced relaxations, whereas nitroprusside-induced relaxations were unaffected by D600. CONCLUSION: Thus, endothelium-dependent relaxation is more dependent on [Ca(2+)](o) than endothelium-independent relaxation, and it seems likely that [Ca(2+)](o) plays an important role not only in contractile processes, but also in relaxant processes as well.
Authors: I Rinner; H N Doods; K J van Charldorp; D Davidesko; P A van Zwieten Journal: Naunyn Schmiedebergs Arch Pharmacol Date: 1988-02 Impact factor: 3.000
Authors: Giovana Vechi; Priscila de Souza; Luísa Mota da Silva; Sérgio Faloni de Andrade; Valdir Cechinel Filho; Rita de Cássia Melo Vilhena de Andrade Fonseca Da Silva Journal: 3 Biotech Date: 2019-11-11 Impact factor: 2.406