Age-dependent alterations in vascular smooth muscle cell responsiveness to platelet-derived growth factor in genetic hypertension.

1. This study examined and compared the growth characteristics of vascular smooth muscle cells (VSMC) isolated from 4 and 12 week old spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats following stimulation with platelet-derived growth factor-BB (PDGF-BB). 2. Vascular smooth muscle cells from 4 week old SHR proliferated at a slower rate than VSMC isolated from 12 week old SHR (1.08 +/- 0.06/day vs 1.89 +/- 0.13/day respectively, P < 0.05). In contrast, there was no difference in the proliferation of VSMC from 4 and 12 week WKY rats (0.62 +/- 0.06/day vs 0.82 +/- 0.13/day, respectively, P > 0.05). 3. The cell density at which VSMC from 4 and 12 week old SHR become refractory to the mitogenic effects of PDGF-BB was similar and approximately two-fold greater than VSMC from age-matched WKY rats. 4. This study concludes that there is an age-dependent, differential and specific upregulation of growth rate mechanisms in VSMC from SHR which enhance proliferation in response to PDGF-BB.