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 (× 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 cells in the total 22Na+ washout rate constant (× 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.
Received April 6, 1987; revision accepted September 14, 1987.
Address correspondence and reprint requests to Dr. A. Aviv at Hypertension Research Center, Room F-578 MSB, University of Medicine & Dentistry of N.J., 185 South Orange Avenue, Newark, NJ 07103, U.S.A.
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