Lymphatic absorption of fatty acids and cholesterol in the neonatal rat

High-fat diets are essential in suckling animals to ensure adequate calorie s for postnatal growth, but their lymphatic transport of dietary lipids has not been characterized. We established a lymph fistula model in suckling r ats to quantify intestinal uptake and lymphatic transport of dietary lipids and analyzed lipoprotein fractions. Suckling 19-day-old Sprague-Dawley rat s had their mesenteric lymph ducts cannulated and gastroduodenal tubes inse rted. After overnight recovery, [H-3]triolein and [C-14]cholesterol were in fused for 6 h. Of the total dose, only 38% of triolein and 24% of cholester ol were transported in the lymph of suckling rats. Analyses of residual lum inal contents and intestinal mucosal homogenate showed neither reduced abso rption nor delayed mucosal processing of ingested lipids to be the cause. T hin-layer chromatographic analysis of radioactive mucosal lipids, however, showed a predominance of free fatty acids (60%) and free cholesterol (67%), implying impaired esterification capacity in these animals. We speculate t hat this reduced esterification allows for portal transport or direct enter ocyte metabolism of dietary lipids.