Metabolism of long-chain fatty acids, alcohols and alkylglycerols in the fish parasite Paratenuisentis ambiguus (Acanthocephala)

Abstract

Specific differences between the acyl composition of lipids of the helminth Paratenuisentis ambiguus and its host eel, as shown previously, prompted us to study the lipid metabolism in this intestinal fish parasite. Adults and larvae of P. ambiguus were fed various lipid precursors, e.g., fatty acids, long-chain alcohols and 1-O-alkylglycerols, which may occur as common nutrients of intestinal parasites. Incorporation of [1-14C]palmitic acid into neutral and polar lipids was found to be similar under aerobic and near-anaerobic conditions. In adult parasites maintained in culture medium supplemented with glucose, [1-14C]palmitic acid was incorporated mainly into triacylglycerols and phosphatidylcholines, whereas [1-14C]oleic acid was incorporated preferentially into triacylglycerols. In fasted adults, as well as in larvae, [1-14C]oleic acid was mainly transferred to phosphatidylcholines. Lipolytic activity was detected in adult parasites that had been incubated with radioactive trioleoylglycerol. [1-14C]Hexadecan-1-ol was oxidized in P. ambiguus at a high rate to labeled palmitic acid, which was incorporated into various lipid classes of P. ambiguus. Small but significant proportions of radioactivity from hexadecan-1-ol were incorporated into ether glycerolipids of the parasite. A more direct precursor in ether glycerolipid metabolism, i.e., rac-1-O-[1'-14C]hexadecylglycerol, was incorporated into alkyl and 1'-alkenyl moieties of choline and etha-nolamine ether-glycerophospholipids of P. ambiguus in high yield. High proportions of labeled diacylglycerols, triacylglycerols and steryl esters were detected in surface lipids as well as lipid extracts of the culture media after incubation of P. ambiguus with [1-14C]palmitic or [1-14C]oleic acids.(ABSTRACT TRUNCATED AT 250 WORDS)