Turnover of protein and diacylglycerol components of lipophorin in insect haemolymph

Abstract

Lipophorin, radiolabelled in the protein or diacylglycerol moiety, was purified from adult locusts injected previously with [ 14C]protein hydrolysate or sodium[1- 14C]palmitate. The radiolabelled lipophorin was injected into adult male locusts and haemolymph samples taken periodically to determine the rate of disappearance of radioactivity from the haemolymph. Lipophorin was also purified from locusts that had been injected four days previously with ([ 14C]protein)-lipophorin to demonstrate that the radioactivity observed in the haemolymph at this time is due to radiolabelled lipophorin. The results indicate that the half-life of the protein component of lipophorin in resting insects is about 5–6 days whereas that of the diacylglycerol component is only about 2–3 hr. The results are consistent with the hypothesis that lipophorin functions as a “reusable shuttle” to transport a variety of lipid classes between sites of absorption, storage and utilisation.