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Mitogenesis in Cultured Vascular Smooth Muscle Cells from Two Rat Models of Hypertension in Response to Fetal Calf Serum and Angiotensin II

Hypertension may result from vascular hypertrophy or hyperplasia due to enhanced growth of vascular smooth muscle cells (VSMCs), which has been demonstrated in VSMCs from spontaneously hypertensive rats (SHRs) compared to Wistar-Kyoto (WKY) rats. To determine whether this enhanced mitogenesis is peculiar to SHRs or a general phenomenon in genetic models of hypertension, we have measured indices of cell growth [3H]-thymidine uptake in VSMCs from SHRs and New Zealand genetically hypertensive (GH) rats and controls [WKY and normal Wistar (N) rats] cultured in fetal calf serum (FCS) or angiotensin II (Ang II, 0.1 μM) in either 3% heat-treated FCS or serum-free medium. SHR cell numbers increased faster in response to both mitogens compared to WKY rats. However, GH and N rat responses to FCS were the same. Ang II caused a significant but similar increase in cell numbers in both GH and N rat cells (i.e., Ang II caused hyperplasia in all four strains) but [3H]thymidine uptake was significantly greater in GH rat cells. Ang II increased the total well protein content but not protein normalized on cell number, i.e., no hypertrophie effect of Ang II was seen in these actively dividing cells. We conclude that (a) growth properties of VSMCs from rats with genetic hypertension vary between strains; the differences in growth may reflect strain-specific variation in the activity of intracellular signalling systems subserving mitogenesis; and (b) Ang II causes VSMC hyperplasia.