²²Na⁺ and ⁸⁶Rb⁺ transport in vascular smooth muscle of SHR, Wistar Kyoto, and Wistar rats

To gain further insight into differences in cellular Na+ and K+ regulation between the spontaneously hypertensive rat (SHR), Wistar Kyoto (WKY), and American Wistar (W) rats, 22Na+ and 86Rb+ washouts were performed under steady-state conditions in cultured vascular smooth muscle cells from the three rat strains. SHR vascular smooth muscle cells showed significantly higher bumetanide sensitive 86Rb+ washout rate constant (x 10-4/min; mean ± SEM) than WKY cells (-38.6 ± 2.84 and -23.8 ± 3.58, respectively; p < 0.005). SHR vascular smooth muscle cells also exhibited significantly higher values than WKY in cells in the total 22Na+ washout rate constant (x 10-2/min) (-61.0 ± 1.57 vs. -53.8 ± 1.24; p < 0.005). The amiloride sensitive component of the 22Na+ washout rate constant accounted for these differences (-18.6 ± 1.04 for SHR and -12.1 ± 2.00 for WKY; p < 0.05). There were no apparent differences in cellular Na+ concentrations between WKY and SHR cells. In general, the 86Rb+ and 22Na+ washout parameters of W rat cells were quite similar to those of cells from SHR. We conclude that the bumetanide-sensitive 86Rb+ washout (the Na+ K+-cotransport), the overall, and the amiloride-sensitive 22Na+ washout (the latter primarily represents the Na+/H+ antiport) are higher in SHR than WKY rat vascular smooth muscle cells. These findings indicate innate differences in cellular Na+ and K+ transport in vascular smooth muscle cells of the SHR and WKY rat. The mechanisms responsible for these differences are yet to be determined.

Duke Scholars

Author Thomas Norton Denny Medicine, Duke Human Vaccine Institute