Abstract: 【Aim】 Lipophorin is a vital hemolymph lipoprotein, which delivers 90% of lipids to internal organs. This study aims to investigate the lipophorin composition during late larval， pupal and adult stages of the silkworm， Bombyx mori. 【Methods】 The compositional changes of hemolymph lipoprotein during various metamorphic stages were tested using potassium bromide density gradient ultracentrifugation, heparin sodium precipitation, and high performance liquid chromatography coupled with evaporative light scattering detector (HPLC-ELSD) methods. 【Results】 During the transition from the 5th instar larva to adult， the isolated lipophorin density was 1.130 g/mL in larval stage and 1.139 g/mL in spinning stage, but decreased in pupal stage (1.083 g/mL). The lipophorin subspecies estimated using a heparin sodium precipitation method showed that high density lipophorin was predominant (9.8 μg/μL) in the spinning stage. Low density lipophorin was increased from spinning stage and constantly present in pupal stage (4.2 μg/μL). Meantime the apolipophorin III content was low in all metamorphic stages and reached the highest in 2-day-old pupa (4 μg/μL). On the other hand, total lipid concentration gradually increased from the spinning stage to pupal stage (from 0.5 to 3.8 μg/μL). Neutral lipid composition estimated by HPLC-ELSD showed that monoacylglycerol was trace amount in all stages (<0.04 μg/μL). Diacylglycerol was noted in mid-5th instar larval to end of pupal stage (0.11-0.61 μg/μL), and triacylglycerol was found in pupal stage (0.18-1.02 μg/μL). 【Conclusion】 Overall results indicated that high density lipophorin mainly transported diacylglycerol during larval and spinning stages. After pupation, high density lipophorin was associated with more triacylglycerol than diacylglycerol, and with apolipophorin III to form the low density lipophorin. These observations suggest that lipophorin conversions are precisely timed processes.

Key words:  Bombyx mori, lipophorin, high density lipophorin (HDLp), low density lipophorin (LDLp), lipid