Altered Calcium Current of the Vascular Smooth Muscle in Renal Hypertension

Altered Calcium Current of the Vascular Smooth Muscle in Renal Hypertension

<P> The present study was aimed at investigating whether the calcium current in the vascular smooth muscle (VSM) cells is altered in renal hypertension. Two-kidney, one clip (2K1C) and deoxycorticosterone acetate (DOCA)-salt hypertension were made in Sprague-Dawley rats. Rats without clipping the renal artery or implanting DOCA were used as control for 2K1C and DOCA-salt hypertension, respectively. Four weeks after clipping, systolic blood pressure was significantly higher in 2K1C rats than in control (192&#8273;24 and 119&#8273;4 mmHg, respectively, n=16 each). DOCA-salt rats also showed a higher blood pressure (180&#8273;15 mmHg, n=18) compared with control (121&#8273;6 mmHg, n=14). VSM cells were enzymatically and mechanically isolated from basilar arteries. Single relaxed VSM cells measured 5∼10 μm in width and 70∼150 μm in length were obtained. VSM cells could not be differentiated in size and shape between hypertensive and normotensive rats under light microscopy. High-threshold (L-type) calcium currents were recorded using whole-cell patch clamp technique. The amplitude of the current recorded from VSM cells was larger in 2K1C hypertension than in control. Neither the voltage-dependence of the calcium current nor the cell capacitance was significantly affected by 2K1C hypertension. By contrast, the amplitude of the calcium current was not altered in DOCA-salt hypertension. These results suggest that high-threshold calcium current of the VSM cells is altered in 2K1C hypertension, and that calcium channel may not be involved in calcium recruitment of VSM in DOCA-salt hypertension.