STIMULATION OF CULTURED VASCULAR SMOOTH-MUSCLE CELL-PROLIFERATION BY THROMBOSPONDIN IS POTENTIATED BY ZINC

The interaction of zinc sulfate with thrombospondin (TSP) derived from bovine platelets, on the proliferation of bovine aortic smooth muscle cells was investigated using cell culture. Zinc alone has no effect b ut potentiates the stimulatory effect of TSP on the incorporation of [ H-3]thymidine into the acid-insoluble cell fraction. Other heavy metal s including copper, lead, manganese and nickel did not exhibit a simil ar effect. In bovine aortic endothelial cells, [H-3]thymidine incorpor ation was stimulated by zinc alone and suppressed by TSP alone; the st imulation by zinc was significantly reduced by TSP. In human fibroblas tic IMR-90 cells, [H-3]thymidine incorporation was stimulated by eithe r zinc or TSP; a simultaneous treatment with zinc and TSP showed an ad ditive effect. The present data suggest that zinc may be a unique heav y metal that potentiates the proliferation of vascular smooth muscle c ells stimulated by TSP; in addition, such an interaction was observed selectively in this cell type. Since a large amount of TSP is released from alpha-granules of aggregated platelets, zinc mag augment TSP act ivity which is involved in the physiology of vascular tissues.