Serum lipoprotein composition, platelet factor and arterial smooth muscle cells.

The incorporation of [3H] thymidine and the synthesis of glycosaminoglycans (GAG) by cultured human aortic smooth muscle cells were studied in the presence of human sera with high HDL cholesterol concentration, high LDL cholesterol concentration or with normal serum lipoprotein concentrations. The sera were prepared either conventionally (CPS, platelet factor present) or from platelet poor plasma by recalcification (PPPS). As compared to normolipidaemic sera, HDL-aemic CPS decreased the incorporation of thymidine but LDL-aemic sera had no effect. HDL-aemic sera decreased markedly the synthesis of sulphated GAG but had no effect on the synthesis of hyaluronic acid (HA). Therefore, the sulphated GAG/HA ratio was decreased. The decrease in sulphated GAG was observed only in the presence of CPS, not in the presence of PPPS. LDL-aemic sera decreased the synthesis of hyaluronic acid causing an increase in the sulphated GAG/HA ratio. This effect was observed in the presence of both CPS and PPPS. The results suggest that determination of the sulphated GAG/HA ratio in aortic smooth muscle cell cultures provides a useful method for estimating the atherogeneity of various sera. The anti-atherogenic effect of HDL-aemic sera seems to be dependent on the platelet factor while the atherogenic effect of LDL-aemic sera may be independent of the platelet factor.