Multiplication-stimulating activity (MSA) stimulates proteoglycan synthesis in cultured endothelial cells.

Cultured endothelial cells have previously been shown to have specific binding sites for certain insulin-like growth factors (IGFs) and insulin. In the present study, the IGF, Multiplication Stimulating Activity (MSA), at concentrations of 100-1000 ng/ml, stimulated 35SO4 incorporation into proteoglycans by endothelial cells cultured from bovine pulmonary arteries. The stimulatory effect on proteoglycan synthesis was not accompanied by changes in cell number, total protein synthesis, nor collagen synthesis and was not mimicked by insulin. These findings suggest that MSA specifically stimulated accumulation of proteoglycans in the cultured endothelial cells, with the effect mediated through an IGF receptor.