Increased lymphatic flux of hyaluronan from cat intestine during fat absorption

During fat absorption, chylomicrons with sizes up to 5,000-10,000 A must traverse an interstitium that has estimated pore sizes of 120-200 A to reach the lacteals. The present experiments were performed to study the behavior of the interstitial matrix component hyaluronan during fat absorption from the intestine. Ileal segments were isolated and autoperfused in pentobarbital-anesthetized cats. A postnodal lymphatic was cannulated, and lymph flow, protein, and hyaluronan concentration in lymph were determined. In group 1, a mixture of oleic acid and taurocholate was infused into the ileal lumen, while in group 2 the animals were fed cream overnight. In group 1, control lymph flow and hyaluronan concentration averaged 53.3 +/- 16.0 (SD) microliters.min-1.100 g intestine-1 and 21.4 +/- 16.0 micrograms/ml, respectively. Administration of taurocholate and oleic acid increased lymph flow and lymph hyaluronan concentration by 100 and 50%, respectively, resulting in a nearly three-fold increase in hyaluronan flux. Subsequent increases in venous pressure increased lymph flow and reduced hyaluronan concentration in lymph to less than 3 micrograms/ml. Hyaluronan flux remained approximately 2 micrograms.min-1.100 g intestine-1 independent of lymph flow. In group 2, no lymph sample was available before administration of fat. Hyaluronan concentration at control venous pressure was 19.3 +/- 6.7 micrograms/ml and fell to 10 micrograms/ml at the highest lymph flow. Hyaluronan flux was approximately 10 micrograms.min-1.100 g intestine-1 at the highest lymph flow and venous pressure (P less than 0.05 compared with the same lymph flow in group 1).(ABSTRACT TRUNCATED AT 250 WORDS)