Flow cytometric analysis of cell cycle of cultured aortic smooth muscle cells from two strains of genetically hypertensive rats.

The growth curves of aortic smooth muscle cells (SMCs) from spontaneously hypertensive rats (SHRs) and their normotensive controls, Wistar-Kyoto (WKY) rats, and genetically hypertensive (GH) rats and their normotensive outbred controls (N) were compared. The proportion of cells in the various phases of the cell cycle was measured by flow cytometry. SHR cells showed significantly shorter doubling time than WKY rat cells, but doubling times for GH and N rats did not differ and were nearly the same as for SHRs. SHRs showed significantly greater proportion of S-phase (DNA-synthesizing) cells compared to WKY rat cells in the exponential growth phase. No significant difference was observed between GH and N rats in the proportion of cells in other phases of the cell cycle. GH and N rat cells stopped dividing in fetal calf serum (FCS)-free Dulbecco's Modified Eagle Medium (DMEM), whereas SHR and WKY rat cells continued to progress through the cell cycle in serum-free DMEM. The responses of FCS-deprived-arrested cells to the addition of FCS were similar in GH and N rats. SHRs showed a prolonged increase in S-phase cells in response to FCS compared to WKY rat cells, but maximum effects were similar. Enhanced cell proliferation in SHRs is not present in the other hypertensive strain of rats and is not explained by a simple hyperresponse to FCS.