Effect of the chloride channel activity on vascular tone in the spontaneously hypertensive rats

AIM: To study the chloride channel activity ［ICl(Ca)］ in vascular smooth cells of the spontaneously hypertensive rats (SHR). METHODS: The vascular beds of mesenteric arteries were isolated from the pentobarbital anesthetized rats and perfused with 37 ℃ PSS at a constant flow rate. The vasoconstriction response to norepinphrine (NE) was determined by changes in perfused pressure. The strips of the rat arteries were mounted in an organ chamber filled with 37 ℃ PSS and the vascular tension was measured. RESULTS: (1) The contractile responses of mesenteric arteries to NE in SHR were greater than that in Wistar rats. (2) The inhibitory magnitude of the contractile response by niflumic acid in SHR was significantly less than that in Wistar rats and showed dose-dependent manner. (3) Decreasing the extracellular Cl- concentration increased the contractile response to NE significantly and the amplitude of enhanced contractile response in SHR was greater than that in Wistar rats. CONCLUSION: It can be concluded that NE-induced contraction is enhanced in SHR, which is partly due to an increase in Cl- efflux through the Ca2+-activated Cl- channels. The chloride channel activity may increase in association with the elevation of vascular tone and blood pressure.