LIPID TRANSFER FROM INSECT FAT-BODY TO LIPOPHORIN - COMPARISON BETWEEN A MOSQUITO TRIACYLGLYCEROL-RICH LIPOPHORIN AND A SPHINX MOTH DIACYLGLYCEROL-RICH LIPOPHORIN

Two insect lipoproteins, triacylglycerol-rich Aedes aegypti lipophorin and diacylglycerol-rich Manduca sexta lipophorin, were compared in th eir ability to load neutral lipid from fat body. when fat body of M. s exta was incubated in vitro with [H-3]oleic acid, all radiolabeled fat ty acids were esterified, predominantly to triacylglycerol. In A. aegy pti fat body, however, half of the label remained as free fatty acids. When A. aegypti fat body was radiolabeled with [H-3]glycerol, most of the radiolabel was incorporated in triacylglycerol. When either A. ae gypti or M. sexta lipophorin was incubated with A. aegypti fat body, l abeled with [H-3]oleic acid, both lipophorins incorporated mainly radi olabeled free fatty acids, while almost no radiolabeled glycerides wer e transferred. When the same experiment was performed with A. aegypti fat body, radiolabeled with [H-3]glycerol, very little transfer of rad iolabeled glycerides was detected. In contrast, when either M. sexta o r A. aegypti lipophorin was incubated with M. sexta fat body, both lip ophorins incorporated neutral lipids, predominantly diacylglycerol. A. aegypti lipophorin incorporated half the amount of radiolabeled lipid , compared to M. sexta lipophorin. Lipophorins from both species were treated with triacylglycerol lipase of the yeast Candida cylindracea. Although this lipase readily delipidated M. sexta HDLp, it was not abl e to remove triacylglycerol from A. aegypti HDLp. The data presented s uggest that, under the conditions used, lipid transfer from fat body t o lipophorin in A. aegypti is not as efficient as in M. sexta.