Growth and nhe-1 protein levels in cultured vsmc from dahl salt-sensitive rats

Cultured VSMC from the SHR exhibit faster growth rates that are associated with greater Na/H antiporter activity and increased protein levels of the NHE-1 isoform of the Na/H antiporter, as compared to cells from WKY rats (J. Am. Soc. Nephrol. 5(3): , 1994). Whether VSMC from other genetic models of hypertension display enhanced growth in vitro is unknown. The present study examined growth rates and the relative abundance of NHE-1 protein in cultured VSMC from Dahl salt sensitive (DS) and salt resistant (DR) rats. VSMC were isolated from aortas of DS and DR rats that were kept on a 1% salt diet. The blood pressure of DS rats was higher than DR prior to the establishment of cell cultures (159+7 vs 94±8 mm Hg, p<0. 001). Cultured VSMC (studied in passages 4-7) from DS grew faster than those from DR as shown by shorter doubling times (20. 6 ±1. 0 vs 25. 1+1. 8 hrs, respectively, p<0. 05) and increased thymidine incorporation (1233±125 vs 917±97 cprn/IOOO cells, respectively, p<0. 05). Leucine incorporation was also greater in cells from DS than DR rats (251±20 vs 181±18 cpm/1000 cells, respectively, p<0. 025). The relative abundance of the NHE-1 isoform of the Na/H antiporter was determined by Western blotting with affinity purified antibodies. There was an apparent increase (about 50%) in NHE-1 protein levels in VSMC from DS than cells from DR rats (0. 309±0. 66 vs 0. 216+0. 94 O. D. units/10 ng protein, n=, respectively), although this was not statistically significant. We conclude that cultured VSMC from DS rats grown in early sub-passages in culture, display a hyperplastic phenotype similar to that reported in cultured VSMC from the SHR. Like in the SHR, this hyperplastic response in the DS rat may be associated with increased abundance of NHE-1 protein levels.