ORALLY FED DIGALACTOSYLDIACYLGLYCEROL IS DEGRADED DURING ABSORPTION IN INTACT AND LYMPHATIC DUCT CANNULATED RATS

Membrane lipids of green plants digalactosyldiacylglycerol (DGalDG) an d monogalactosyldiacylglycerol (MGalDG) are hydrolyzed in vitro by hum an duodenal contents, pancreatic juice and bile salt stimulated lipase and guinea pig and rat pancreatic lipase-related protein 2 to free fa tty acids, di-and monogalactosylmonoacylglycerols and water soluble ga lactose-containing compounds. The fate of intermediate products is unk nown. We have investigated the digestion and absorption of DGalDG in r ats. [H-3]- and [C-14]-labeled DGalDG in galactolipid dispersions, and 200 g/L soybean triacylglycerol (TG) oil-galactolipid emulsions of di fferent concentrations were fed orally to intact and lymphatic duct ca nnulated rats. Chyle, gastrointestinal tract, liver and plasma were an alyzed for radioactivity in different lipid classes. Recovery of [H-3] also was determined in feces, Comparison was made with an emulsion of [C-14]dipalmitoyl-phosphatidylcholine ([C-14]DPPC), soybean TG oil an d soybean phosphatidylcholine (PC). Less than 2% of the radioactivity in chyle was found in DGalDG, >70% of the radioactivity in triacylglyc erol (TG), and the remaining part in glycerophospholipids. In intact r ats, <1.5% of radioactivity in liver and plasma was identified as DGal DG. In experiments where 120 mg galactolipid-phospholipid mixture or 1 20 mg PC were given in a soybean TG oil-emulsion, the absorption of ga lactolipid fatty acids was less complete than PC-fatty acids, as indic ated by analysis of feces and intestinal contents. Galactolipids are n ot absorbed intact or as reacylated monoacyl compounds by rats.