Altered chloride transport in arteries from aldosterone salt-hypertensive rats

Chronic infusion of d-aldosterone into uninephrectomized rats on high sodium intake resulted in a significant increase in systolic blood pressure. The steady state efflux of 36Cl in aorta and femoral artery of hypertensive rats was significantly elevated compared to that in arteries of control rats. These elevations in chloride efflux persisted in the presence of the Cl-HCO3 exchange inhibitor, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), and in Cl-HCO3 free solution. The Cl-HCO3-dependent component of the 36Cl efflux was also higher under some conditions. DIDS (100 mumol/l), also significantly reduced the increase in 36Cl efflux caused by norepinephrine (NE) in one of four groups, but had no significant effect on the NE stimulated 42K efflux. Contractile responses to both NE and KCl were unaffected by DIDS treatment. Therefore, it appears that Ca influx and release mechanisms function normally in the presence of DIDS. Similarly, DIDS had either a small or no effect on 42K movements under basal conditions. A slight reduction in the passive efflux of 24Na was observed in aortic smooth muscle exposed to DIDS with no significant effect on active Na transport. These findings indicate that DIDS is reasonably selective for Cl exchange sites in vascular smooth muscle during an exposure of 15 min or less and has little effect on cationic transport processes. The application of this blocker as well as anion substitution indicates that an elevation in the 36Cl leak efflux and related Cl permeability of arterial smooth muscle is associated with aldosterone-salt hypertension.