Dose-dependent incorporation of orally infused [1- 14C]oleic acid into the lipid classes of midgut, haemolymph and fat body of dragonfly larvae ( Aeshna cyanea)

Abstract

1. 1. Five different doses of radioactive oleic acid (ranging from 1.87 nmoles to 5.61 μmoles) were administered to Aeshna cyanea larvae. 2. 2. Its incorporation into the midgut epithelium, haemolymph and fat body increased with the dose and time. 3. 3. Low doses caused up to 95% phospholipid labelling in the midgut wall, while labelled triacylglycerol was less than 1%, but increased with the doses to a maximum of 68%. The data favour the glycerophosphate pathway of oleic acid esterification. 4. 4. At low doses oleic acid was mainly released into the haemolymph from the midgut phospholipid pool, and at high doses from the triacylglycerol pool. 5. 5. Diacylglycerol was the most heavily labelled lipid class of the haemolymph, amounting up to 98% and slightly decreasing with time. 6. 6. The fat body showed a dose- and time-dependent increase in labelled phospholipid and triacyl-glycerol, maximally amounting to 14 and 90%, respectively.