Release of granulocyte-specific colony-stimulating activity by human bone
marrow exposed to phorbol esters
SL Gerson and RA Cooper
Granulocyte-macrophage colony growth depends on the presence of colony-
stimulating activity (CSA). Phorbol esters induce concentration- dependent
colony formation in the absence of exogenous CSA. We questioned whether
phorbol esters mimicked the action of CSA by directly stimulating colony
growth, or whether phorbol esters acted indirectly by inducing marrow cells
to release CSA. First, after incubating human bone marrow cells with
phorbol 12,13-dibutyrate (PDB) for 3 days, we separated PDB from the
protein peak of the conditioned medium by Sephadex G-10 gel filtration and
tested this peak for the presence of CSA. When diluted 1:10 in the agar
colony assay, this material induced 133 +/- 15 colonies/10(5) bone marrow
cells. Second, to determine whether bone marrow cells required the
continued presence of PDB in order to release CSA, PDB was removed from
bone marrow cells by washing, and these cells were reincubated in fresh
medium in the absence of PDB. CSA was found in the medium of these
cultures; its release was maximal after preincubation of bone marrow cells
with 5 X 10(-8) M PDB for 3 days, followed by incubation for 3 days in the
absence of PDB. This CSA stimulated granulopoiesis out of proportion to
monocytopoiesis, with 85% +/- 17% of the colonies being granulocytic (as
indicated by histochemical staining for chloroacetate esterase), and 12%
+/- 3% being monocytic (as indicated by nonspecific esterase). Inhibitors
of monocyte colony formation, including PGE1, were not present in the
medium that contained this CSA. These studies demonstrate that normal human
bone marrow cells exposed to PDB release CSA and that this CSA selectively
stimulates granulopoiesis in vitro.
Volume 63,
Issue 4,
pp. 878-885,
04/01/1984
Copyright © 1984 by The American Society of Hematology
