Lymph chylomicron size is modified by fat saturation in rats

Mesenteric lymph chylomicrons were characterized during and after the establishment of steady-state triglyceride transport. Chylomicrons were isolated from lymph at 0, 2, 4, 6, 8 and 12 h after the start of an 8-h infusion of triglyceride emulsion (prepared using either corn or butter oil) at 160 mumol/(kg.h). Lymph flow was not influenced by triglyceride source. Output of triglyceride, measured both in whole lymph and in the chylomicron fraction, was not significantly affected by triglyceride source. Butter oil infusion produced a higher output of chylomicron phospholipid and unesterified cholesterol than was observed in response to corn oil emulsion. Ratios of transported phospholipid to triglyceride for butter oil chylomicrons were higher (1.3- to 1.7-fold) than those for corn oil chylomicrons at every time point examined after the start of lipid infusion. No other compositional differences in chylomicrons due to triglyceride source were observed. These results support the hypothesis that differences in efficiency of absorption and transport between saturated and unsaturated fat are sufficient to explain size differences in secreted chylomicrons in response to corn and butter oil infusions, and suggest that chylomicron number may be influenced by dietary fat saturation.