The particle-free crude extract of differentiated granulocytes (GCE) and the GI-1, GI-2, GI-3 proliferation inhibitory fractions (M.W. ≥ 70,000 ∼ 11,500 and ≤ 4000) were studied for the effects they exert on cultured cells. As shown by the curve, in bone marrow suspension cultures, in the dose range of 0.01-10.0 μg/ml, GCE maximally inhibits 3H-TdR incorporation into the DNA for 5.5 hours. In agar-gel cultures, 1.0-5.0 μg/ml of GCE reduces both the number (by 50.6-54.8%) and the size of the colonies formed. The manifestation of the inhibitory effect of GI-1, GI-2 and GI-3 fractions requires 2.5-3.5 hours. The inhibitors designated GI-2 and GI-3 are target-cell specific but they do not reduce 3H-TdR incorporation either in thymocyte suspension or HeLa monolayer cultures. On the other hand GI-1 inhibits the proliferation in HeLa cultures, as well. These endogenous inhibitors exert their optimum effect, even in a partially purified state at 2-4 orders of magnitude lower concentrations than does 1, 2 5,6-dianhydrogalactitol (DAD), a cell-aspecific inhibitor used for comparison in the same system.
ASJC Scopus subject areas
- Developmental Biology