Association of tissue factor activity with the surface of cultured cells.

Abstract

A C T Tissue factor occurs in a dormant state on the surface of cultured normal human fibroblasts and WISH 1 amnion cells. The activity of undisturbed mono- layers or cells lifted with brief trypsin treatment (0.125% trypsin for 1 min) increases up to 60-fold upon prolonged digestion with dilute trypsin (0.0025% trypsin for 30 min); activity appears subsequent to cell detachment. Up to 70% of the total cellular tissue fac- tor becomes active under these conditions and is re- leased from the cells. The ruthenium red staining coat of the cells is lost during detachment, but cell viability (more than 90% exclude trypan blue) and cell mor- phology do not change during the subsequent develop- ment of tissue factor activity. Furthermore, less than 10% of four intracellular enzymes and less than 20% of two plasma membrane enzymes are released during this period of time. We therefore conclude that cells in culture do have tissue factor activity, that it exists in a latent form, and that total cell disruption is not necessary for this activity to initiate blood coagulation.