Rapid release of fibronectin from human lung fibroblasts by biologically active phorbol esters

A sensitive radioimmunoassay technique has been used to study the effects of several phorbol esters on their ability to release fibronectin from cultured human lung fibroblasts into medium. The biologically active phorbol esters studied rapidly released fibronectin from cells into medium, with concomitant changes in the cellular morphology within 2 h. The quantity of fibronectin released was dose-, time- and promoter-dependent. The earliest release of fibronectin was seen within 30 min of onset of the incubation. Alterations in membrane topology elicited by phorbol esters appear to be responsible for the rapid release of fibronectin molecules from cells into the medium.