A greater stimulation of Na-H antiport in cultured vascular smooth muscle cells by serum from spontaneously hypertensive rats.

We investigated the influence of serum from spontaneously hypertensive rats (SHR) on the Na-H antiport and Na-K pump activity of cultured vascular smooth muscle cells (VSMC). Subjecting the VSMC to rat serum stimulated the ouabain-sensitive 86Rb uptake. This activation of the Na-K pump was significantly greater with the SHR serum than the Wistar-Kyoto rat (WKY) serum. Furthermore, the serum from SHR exhibited a larger Na uptake in the presence of ouabain than that from WKY. A greater 5-(N,N-hexamethylene) amiloride-sensitive Na uptake accounted for this difference. When the Na-K pump was active, serum from either of the two strains did not cause an increase in intracellular Na concentrations. We concluded that serum from SHR produced a more pronounced activation of both the Na-H antiport and the Na-K pump. The study suggests that there are humoral factors in SHR serum which elicit the stimulation of the Na-H antiport, leading to the activation of the Na-K pump of VSMC.