Abstract
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, Na and Rb 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 Rb washout rate constant (× 10/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 cells in the total Na washout rate constant (× 10/min) (−61.0 ± 1.57 vs. −53.8 ± 1.24; p < 0.005). The amiloride sensitive component of the Na 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 Rb and Na washout parameters of W rat cells were quite similar to those of cells from SHR. We conclude that the bumetanide-sensitive Rb washout (the Na K-cotransport), the overall, and the amiloride-sensitive Na 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.