A ROLE FOR A 70-KDA AMINO-TERMINAL FIBRONECTIN FRAGMENT IN SUPPORTINGSOLUBLE GELATIN INTERACTIONS WITH RAT PERITONEAL-MACROPHAGES

Seventy-kilodalton amino-terminal and 180-kDa cell-binding fibronectin fragments were used to determine which fibronectin domains support so luble gelatin interactions with macrophages. At each time measured, in tact and 180-kDa fibronectin supported significantly larger quantities of cell-associated gelatin than control levels (P < 0.05), Throughout the time course fibronectin supported more binding than 180 kDa, Seve nty kilodalton did not augment gelatin binding until 2 h, but by 6 h 7 0 kDa supported more binding than intact fibronectin (P < 0.01), This appeared to result from a cellular response initiated by 70-kDa-gelati n interactions with the macrophages. Within 4 h the majority of gelati n associated with cells under control conditions, and in the presence of fibronectin or 180 kDa, was internalized, Seventy-kilodalton-mediat ed binding remained localized primarily to the cell surfaces at all ti mes, The macrophages partially degraded the internalized and external gelatin fractions, These results demonstrate that intact fibronectin a nd specific fibronectin fragments support soluble gelatin interactions with macrophages.