Growth rate and phospholipase C activity in cardiac and aortic spontaneously hypertensive rat cells

The cellular proliferation rate and phospholipase C sensitivity have been compared in various cardiovascular cells cultured from spontaneously hypertensive (SHR) and Wistar-Kyoto rats (WKY). Aortic smooth muscle cells from SHR showed an enhanced proliferation rate under the culture conditions (in the presence of 10% fetal calf serum) and hypersensitivity to the mitogenic action of angiotensin II and serotonin. Phospholipase C activity (determined by measuring the formation of tritiated inositol phosphates from [3H]-myoinositol) triggered by angiotensin II was also higher in these cells than in those from WKY. Cardiac fibroblasts from SHR proliferated more quickly than those from WKY, which suggests that the increased growth rate is a general feature of SHR cardiovascular cells. Furthermore, as cardiac cells were obtained from newborn animals, this impairment appears to be an intrinsic characteristic of the SHR cells. In contrast, no difference in the phospholipase C reactivity to phenylephrine was found in cardiomyocytes from SHR and WKY. The amount of tritiated inositol monophosphate measured in unstimulated cells, however, was significantly higher in cultures from WKY, which may suggest a difference in the phosphoinositide cycle between both strains of cells. Like the impairment in the proliferation rate, alterations in phosphoinositide metabolism may be a common feature of cardiovascular SHR cells.