title: Lipid digestion in turbot (Scopthalmus maximus) 11: Lipolysis in vitro of (14)C-labelled triacylglycerol, cholesterol ester and phosphatidylcholine by digesta from different segments of the digestive tract.
abstract: Preparations of digesta from the stomach, foregut, hindgut and rectum of turbot (Scophthalmus maximus) were assayed for the ability to hydrolyse glycerol tri[1-(14)C]oleate ((14)C-TAG), 1,2-di[1-(14)C]palmitoyl L-3-phosphatidylcholine ((14)C-PC) and cholesterol [1-(14)]oleate ((14)C-CE) over 1,2,3 and 17h. In the assay of foregut digesta with (14)C-TAG substrate, 37.8% of the total radioactivity was found in the FFA class after the first hour of incubation. This value increased to a maximum of 68.5% of the available label after 17h incubation. Over the same time the proportion of radioactivity in diacylglycerols (DAG, 31.6%-7.4%) decreased while that in the monoacylglycerols increased (MAG, 14.0%-22.3%). In assays of digesta from the hindgut and rectum, after 1 h of incubation, the proportion of radioactivity recovered in FFA represented 64.9% and 74.8%, respectively, whereas the proportions in both DAG and MAG decreased with incubation time. Similarly to (14)C-TAG, the highest rate of lipolytic hydrolysis of (14)C-CE occurred in digesta from the posterior digestive tract where the proportions of radioactivity recovered in FFA of the hindgut (50.0%) and rectum (81.9%) preparations were substantially higher than those of the stomach (3.5%) and the foregut (14.4%) after 1h. With (14)C-PC as substrate the levels of radiolabelled FFA in both the foregut and the hindgut (2.4% and 7.6%, respectively) were markedly lower than the 37.5% in the rectum. The results suggest that the posterior digestive tract is very active in non-specific and phospholipid lipolysis and a region where the major part of lipid digestion takes place.
authors.affiliation: National Center for Mariculture, Israel Oceanographic and Limnological Research Ltd., P.O.B. 1212, Eilat, 88112, Israel.
authors.forename: W M
authors.initials: WM
authors.lastname: Koven
authors.forename: R J
authors.initials: RJ
authors.lastname: Henderson
authors.forename: J R
authors.initials: JR
authors.lastname: Sargent