AJP - Endocrinology and Metabolism, Vol 251, Issue 4 470-E476, Copyright © 1986 by American Physiological Society
Lipoprotein lipase-suppressing mediator in serum of endotoxin-treated rats
G. J. Bagby, C. B. Corll, J. J. Thompson and L. A. Wilson
The conditions under which lipoprotein lipase-suppressing mediator is
present in serum of endotoxin-treated rats was determined in this study.
The suppression of lipoprotein lipase activity in 3T3-L1 cells was used as
a bioassay for mediator in serum. Endotoxin (0.1-10 micrograms/ml) and
serum from control rats did not suppress lipoprotein lipase activity.
Maximum suppression of cell lipoprotein lipase activity (70%) by serum from
endotoxic rats required a cell exposure time of 5 h. At the highest dose of
endotoxin used (1 mg/100 g), significant suppression was achieved when
cells were incubated with 0.5% serum from endotoxic rats (P less than
0.05). Serum obtained 2-3 h after endotoxin injection possessed the maximal
ability to suppress lipase activity, but suppressing activity was not
present in serum collected 8 h after endotoxin. Rats rendered tolerant to
endotoxin by 5 daily injections (0.1 mg/100 g) did not contain detectable
levels of mediator in serum after endotoxin injection. The results
demonstrate that the presence of lipoprotein lipase activity-suppressing
mediator is transitory after in vivo exposure of naive rats to endotoxin,
but does not appear in serum of endotoxin tolerant rats.
