Trypsin enhances erythropoiesis in vitro.

When a single cell suspension of human adult marrow or fetal liver is treated briefly with trypsin, the number of erythroid bursts arising in culture is significantly increased. Erythroid colonies show less stimulation. The time to reach maximum burst number may also be shortened. The absolute increase in burst number is greater at higher concentrations of erythropoietin, suggesting a synergistic effect of trypsin treatment with that of erythropoietin. Trypsin also increases the size of the individual burst subunit. The trypsin effect is not limited to a given class of bursts as distinguished by subunit number. Other enzymes, pronase, chymotrypsin and phospholipase D, also increase burst number but to a lesser degree. The burst-stimulating effect of trypsin is enzymatic since it is completely prevented by DFP, a specific inhibitor of trypsin action.