AJP - Gastrointestinal and Liver Physiology, Vol 242, Issue 3 281-G288, Copyright © 1982 by American Physiological Society
Hepatic stimulator substance: physicochemical characteristics and specificity
D. R. LaBrecque and N. R. Bachur
This laboratory has reported previously that a cytoplasmic extract of
weanling or regenerating adult rat liver (but not normal rat liver) will
produce a 2.5-fold increase in the incorporation of tritiated thymidine
([3H]dThd) into liver DNA of a 34%-hepatectomized test animal. (J. Physiol.
London 248: 273-284, 1975). The present study showed that hepatic
stimulator substance (HSS) will stimulate DNA synthesis in normal adult
rats and CF1 mice as well. The increased incorporation of [3H]dThd into DNA
produced in the normal, nonhepatectomized adult rat was comparable with
that induced by a 34% hepatectomy. Autoradiographic studies revealed that
the [3H]dThd was incorporated into nuclear DNA and that the stimulation
occurred almost exclusively in parenchymal cells. HSS was shown to be heat
stable (100 degrees C for 15 min) and was precipitated but not inactivated
by alcohol. Ultrafiltration and dialysis studies suggested a molecular
weight slightly greater than 10,000. HSS proved to be organ specific,
stimulating the liver but not the kidney, bone marrow, or spleen. HSS was
found to contain no insulin, glucagon, epidermal growth factor, or peptides
of the nonsuppressible insulinlike/multiplication-stimulating activity
(somatomedin) group.
