Properties of endothelial cell and smooth muscle cell cultured in ambient pressure.

Cultures of umbilical vein endothelial cells and smooth muscle cells were studied in a constant pressure chamber. The following results were obtained: (a) Endothelial cell growth was maximal at 80 mmHg and minimal at 0 mmHg (atmospheric pressure) for the first 2 d of incubation. However, these growth rates were reversed during the following 6 d because of steady increase in growth at 0 mmHg, and a decrease in growth at higher pressures. A degeneration of endothelial cells began at 120 mmHg and marked degeneration was noted at 160 mmHg. Growth of smooth muscle cells was not influenced by ambient pressure and a steady increase in labeled nuclei continued throughout the period of culture. (b) Elastin, stainable with tannic acid, was noted electronmicroscopically in both endothelial and smooth muscle cells. (c) Production of prostacyclin by endothelial cells was maximal at 0 mmHg and minimal at 80 mmHg, in contrast to the growth pattern of these cells. Production of thromboxane B2 by endothelial cells and prostacyclin and thromboxane B2 by smooth muscle cells was very slight and not significantly different. Although it is not known at present what mechanism acts on the vascular cells when cultured in ambient pressure, these results may indicate a new concept of the behavioral relationship between endothelial cell, smooth muscle cell, and blood pressure in vivo.