Primary mass cultures and cloned strains of bovine aortic endothelial and smooth muscle cells were investigated with respect to their growth responses to glucocorticoid hormones. The growth of primary endothelial cells was not influenced by glucocorticoid treatment in the absence of fibroblast growth factor (FGF) but was inhibited by about 30% in the presence of FGF; with cloned endothelial cells, glucocorticoids were also growth inhibitory only in the presence of FGF. In contrast, smooth muscle cell growth was inhibited 30%-70% by glucocorticoid treatment in both primary cultures and in the cloned strains in the absence of FGF, and this inhibition was totally abolished by the addition of FGF for both cultures. The corticosteroid influences on cell growth were glucocorticoid specific, concentration dependent, and were observed to be independent of the serum concentration. The results indicate that glucocorticoid hormones have direct and pronounced growth inhibiting effects on aortic smooth muscle cells but only minimal effects on endothelial cells when these components of the vascular wall are analyzed under identical conditions in vitro.

We examined the influence of glucocorticoid hormones on the proliferation of cultured adult bovine aortic smooth muscle cells (BASM) using both primary mass cultures and a cloned strain . Cloned BASM cells maintained on plastic culture dishes were inhibited by -40% by dexamethasone treatment but showed no inhibition when grown on homologous extracellular matrix (ECM) coated dishes. Dexamethasone inhibited growth of primary cultures by 73% on plastic and by 45% on ECM . The inhibitory effect was specific for the glucocorticoids, dexamethasone, corticosterone, and cortisol and was not observed with progesterone, aldosterone, estradiol or 17-a OH progesterone .In cloned cells, the abolition of glucocorticoid inhibition by ECM was independent of seeding density and serum concentration . The inhibition on plastic was dependent on serum concentrations >1% and resulted in both a slow rate of proliferation and a lower saturation density . A specific subset of peptides detected on two-dimensional gels was induced by glucocorticoids under growth inhibitory conditions but was not induced when the cells were grown on ECM .Primary cultures grown on ECM and exposed to Dulbecco's modified Eagle's Medium (DME) containing high density lipoprotein and transferrin grew at 40% of the rate observed for cultures exposed to DME with 10% serum . Both conditions showed growth inhibition of 70% in the presence of dexamethasone . The addition of epidermal and platelet-derived growth factors in DME containing high density lipoprotein and transferrin to cells grown on ECM resulted in growth rates comparable to that observed with cultures exposed to 10% serum and were inhibited 45% by dexamethasone . These results suggest that glucocorticoids inhibit smooth muscle proliferation by decreasing the sensitivity of the cells to mitogenic stimulation by high density lipoprotein when the cells are maintained on a homologous substrate .

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