C. Filipponi et al., METABOLISM OF LONG-CHAIN FATTY-ACIDS, ALCOHOLS AND ALKYLGLYCEROLS IN THE FISH PARASITE PARATENUISENTIS-AMBIGUUS (ACANTHOCEPHALA), Lipids, 29(8), 1994, pp. 583-589
Specific differences between the acyl composition of lipids of the hel
minth Paratenuisentis ambiguus and its host eel, as shown previously,
prompted us to study the lipid metabolism in this intestinal fish para
site. Adults and larvae of P. ambiguus were fed various lipid precurso
rs, e.g., fatty acids, long-chain alcohols and 1-O-alkylglycerols, whi
ch may occur as common nutrients of intestinal parasites. Incorporatio
n of [1-C-14]palmitic acid into neutral and polar lipids was found to
be similar under aerobic and near-anaerobic conditions. In adult paras
ites maintained in culture medium supplemented with glucose, [1-C-14]p
almitic acid was incorporated mainly into triacylglycerols and phospha
tidylcholines, whereas [1-C-14]oleic acid was incorporated preferentia
lly into triacylglycerols. In fasted adults, as well as in larvae, [1-
C-14]oleic acid was mainly transferred to phosphatidylcholines. Lipoly
tic activity was detected in adult parasites that had been incubated w
ith radioactive trioleoylglycerol. [1-C-14]Hexadecan-1-ol was oxidized
in P. ambiguus at a high rate to labeled palmitic acid, which was inc
orporated into various lipid classes of P. ambiguus. Small but signifi
cant proportions of radioactivity from hexadecan-1 ol were incorporate
d into ether glycerolipids of the parasite. A more direct precursor in
ether glycerolipid metabolism, i.e., rac-1-O-[1-C-14]hexadecylglycero
l, was incorporated into alkyl and 1'-alkenyl moieties of choline and
etha-nolamine etherglycerophospholipids of P. ambiguus in high yield.
High proportions of labeled diacylglycerols, triacylglycerols and ster
yl esters were detected in surface lipids as well as lipid extracts of
the culture media after incubation of P. ambiguus with [1-C-14]palmit
ic or [1-C-14]oleic acids. The results suggest that palmitic acid and
oleic acid are incorporated into neutral and polar lipids of P. ambigu
us maintained in glucose medium quite differently with oleic acid show
ing a strong preference for triacylglycerols. However, the incorporati
on of palmitic acid in glucose-fed parasites was similar to that of ol
eic acid in fasted parasites, as well as in larvae. This may be explai
ned by partial fatty acid depletion in fasted worms and rapid cell div
ision in larvae, respectively.