Transfer of lipids between hemolymph and hepatopancreas in the shrimp Macrobrachium borellii

Crustacean lipids are transported in the hemolymph by an HDL. The hepatopancreas is the most important and active organ regarding lipid metabolism, so we studied the interchange of FA and acylglycerols between both components of the hepatopancreas-hemolymph system in the decapod crustacean Macrobrachium borellii. The hepatopancreas and a sole plasma lipoprotein were labeled by in vivo incubations with 14C palmitic acid injected into the hemolymph. Then they were incubated in vitro with unlabeled hepatopancreas and hemolymph, and the transfer of lipids between them was measured by radiochromatographic techniques. It was determined in vivo that more than 80% of the circulating palmitic acid was taken up by the hepatopancreas and incorporated into PC and TAG. Both classes of lipids, but mainly PC, were transferred back from tissues to the hemolymph. Lipid transfer was also demonstrated in vitro. The transfer of PC (30% of labeling) as well as that of FFA (48% of labeling) from hemolymph to hepatopancreas was determined. On the other hand, FFA were released more efficiently than the acylglycerols from intact hepatopancreas to hemolymph, and they were the only lipid transferred when the hepatopancreas had been previously washed.