Four-week-old broiler chickens were injected intravenously with from 0.01 to 1 mg of E. coli endotoxin/kg body weight or with saline. 2. At all doses used endotoxin markedly depressed food intake and lipoprotein lipase activities in muscle and adipose tissue within 8 h. Heart lipoprotein lipase activity was significantly depressed only at doses of 0.1 mg endotoxin/kg body weight or greater. 3. Treatment of birds with 0.3 mg endotoxin/kg body weight reduced post-heparin lipoprotein lipase activity to 0.13 of that in control birds in 8 h. 4. Endotoxin generally depressed plasma very-low-density lipoprotein concentration. Plasma non-esterified fatty acid concentration was significantly elevated only in birds given 1 mg endotoxin/kg body weight. 5. Fatty acid synthetase activity in the liver of endotoxin-treated birds was significantly lower than in control birds 16 h after administration of endoxin, but not after 8 h. 6. These results show that tissue lipoprotein lipase activity in birds is very responsive to E. coli endotoxin, as in mammals. Hypertriglyceridaemia occurs only occasionally in endotoxin-treated chickens, most probably because of the particularly close relationship between food intake and hepatic lipoprotein synthesis in birds.
