AJP - Gastrointestinal and Liver Physiology, Vol 242, Issue 3 289-G295, Copyright © 1982 by American Physiological Society
In vitro stimulation of cell growth by hepatic stimulator substance
D. R. LaBrecque
An extract of normal weanling or adult regenerating rat liver called
hepatic stimulator substance (HSS) stimulates incorporation of tritiated
thymidine ([3H]dThd) into liver DNA. In vivo, it is organ specific, species
nonspecific, displays diurnal rhythm, and has a molecular weight of
approximately 10,000-20,000. It has now been further characterized in
vitro. HSS retained organ specificity, stimulating normal adult hepatocytes
in primary culture, the HTC, PLC, and MH1C1 hepatoma cell lines, and the
PRC rat liver cell line. It did not stimulate human or mouse lymphocytes,
3T3 mouse fibroblasts, Y1BS1 mouse adrenal cells, Chinese hamster ovary
cells, rat hypernephroma cells, C6 rat glial cells, or L1210 mouse leukemic
cells. More detailed studies of the response of HTC cells to HSS revealed a
dose-dependent increase in [3H]dThd incorporation (up to 30-fold) with a
response to as little as 140-ng purified extract/ml culture medium.
Autoradiography confirmed that the thymidine was taken up by nuclear DNA.
This represented a true stimulation of growth as shown by an almost twofold
increase in cell number after 6 days of exposure to low doses of HSS.
