Cortisol and lysosomal stability in normal and atheromatous rats

Effect of cortisol on the proliferation and protein synthesis of human aortic smooth muscle cells in culture

The synthesis of collagen (measured as the formation of non-dialyzable hydroxyproline) and other proteins, and the activity of lysyl oxidase, the enzyme responsible for the formation of cross-links in elastin and collagen, were measured in cultured human aortic smooth muscle cells in the presence of various cortisol concentrations. In addition, the effect of cortisol on the proliferation of the cells was also studied. At concentrations of 10(-6) M and greater, cortisol retarded cell growth markedly, as judged by decreased incorporation of 3H-thymidine by the cells and decreased DNA content of the cultures. At the same concentrations, cortisol increased the synthesis of collagen and other proteins. The magnitude of the increase was similar for collagen and other proteins. The activity of lysyl oxidase was also increased in the presence of 10(-6) and 10(-5) M cortisol, but to a lesser extent than the synthesis of collagen. Other studies using cultured cells have shown that cortisol decreases the synthesis of hyaluronic acid but not of sulphated glycosaminoglycans by smooth muscle cells and does not injure endothelial cells. Considering these findings in the light of the present results, it is suggested that cortisol induces changes in the metabolism of connective tissue macromolecules of smooth muscle cells that can be regarded as atherogenic. However, some other important biological changes associated with atherogenesis (smooth muscle cell proliferation and endothelial injury) do not occur in vascular cells exposed to cortisol.

The stabilizing effect of glucocorticoids on human endothelial cells in culture

The effect of hydrocortisone, prednisolone and dexamethasone on the stability and viability of cultured human endothelial cells was studied by measuring the release of 51Cr from pre-labelled cells by cell number calculation and by the Trypan-blue test. All glucocorticoids studied, stabilized endothelial cells as demonstrated by a decreased release of 51Cr. The maximal stabilizing effect of the steroids appeared to be equal, although the maximal effect of dexamethasone was seen at a lower concentration than that of prednisolone and hydrocortisone. However, at the very high concentration of 10(-4) mol/l, dexamethasone induced an increase in the release of 51Cr suggesting a toxic effect. The viability of cells was not affected by the steroids. The stabilizing effect of glucocorticoids at optimal concentrations in vitro may indicate strengthening of endothelial integrity by the steroids in vivo. This may explain their beneficial effect in the treatment of certain vascular disorders, e.g. thrombocytopenia.