Lipoprotein lipase-suppressing mediator in serum of endotoxin-treated rats.
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.
D000818:Animals; D001681:Biological Assay; D001769:Blood; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance; D004731:Endotoxins / Q000494:pharmacology*; D004926:Escherichia coli; D007700:Kinetics; D008071:Lipoprotein Lipase / Q000037:antagonists & inhibitors* / Q000097:blood; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D004731:Endotoxins; D008071:Lipoprotein Lipase