Wax Esters in Fish: Absorption and Metabolism of Oleyl Alcohol in the Gourami (Trichogaster cosby)

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Abstract
Absorption and subsequent metabolism of oleyl alcohol and oleic acid in the female gourami (Trichogaster cosby) were compared by feeding the 1-3H2- or U-14C-labeled compounds. Lipids of intestines, blood, liver, body and roe were analyzed at time intervals over a period of 24 hours after ingestion. Absorption of both alcohol and acid was 60 to 70% of the amount offered. Alcohol was largely oxidized to acid in the intestinal tissue, but some of it was esterified to form wax ester. The relative extent to which these processes took place depended on the amount of alcohol fed. Dietary acid did not give rise to alcohol or wax esters in the intestines. Free alcohol did not enter the blood stream in any appreciable amount, but wax esters were found in the blood lipids. Some of these wax esters were deposited with body and roe lipids. Liver lipids, however, contained free alcohol besides wax ester which indicates that they are subject there to further metabolism probably involving oxidation of the alcohol moiety. The liver seems to have mainly a corrective function when the digestive and circulatory systems are overloaded with wax esters. Body wax esters are < 1% of the total body lipids in the gourami and intestinal wax esters are a major source for them. Roe wax esters are 85% of the roe lipids, but only a minor part of them originates from intestinal wax esters. The greater portion of roe wax esters is synthesized in the roe where the chains of the dietary oleyl alcohol or oleic acid are used equally efficiently in spite of the intermediary oxidation of the former.