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Department of Physiology and Biophysics, Louisiana State University Medical Center, Shreveport, LA 71130 * Ross Products Division, Abbott Laboratories, Columbus, OH 43215
To evaluate the hypothesis that stimulation of intestinal apolipoprotein (apo) AIV by dietary fat depends upon assembly and transport of chylomicrons, we examined the effect of duodenal infusion of fatty acids of graded chain length on mucosal synthesis and lymphatic output of lipid and apo AIV. Rats with duodenal cannulas and mesenteric lymph fistulas were given 8-h duodenal infusions of lipid emulsions containing either butyric (4:0), caprylic (8:0), lauric (12:0), myristic (14:0), stearic (18:0), oleic (18:1), linoleic (18:2) or arachidonic (20:4) acids, or tributyrin, tricaprylin or triolein. Lymph outputs of triglyceride, phospholipid and apo AIV were measured at 0, 2, 4, 5, 6, 7 and 8 h after the start of lipid infusion. Significant increases in lymph lipid (triglyceride, phospholipid) and apo AIV output were observed in response to long-chain fatty acids (14:0, 18:0, 18:1, 18:2, 20:4) or triolein; short- or medium-chain fatty acids (4:0, 8:0, 12:0) or tributyrin or tricaprylin produced no significant increase in lymph lipid output above basal levels. Similarly, increased jejunal mucosal synthesis of apo AIV was observed in response to duodenal infusion of oleic acid but not butyric or caprylic acid. These results provide direct support for the hypothesis that stimulation of apo AIV by dietary fat depends upon transport of absorbed lipid via chylomicrons in lymph.
KEY WORDS: rats chylomicrons lipoproteins
1 Presented in part at Experimental Biology 95, April 1995, Atlanta, GA [Kalogeris, T., Monroe, F., Chen, Q. & Tso, P. (1995) Lymphatic output of lipid and apolipoprotein AIV vary with chain length of intestinally-infused fatty acid. FASEB J. 9: A367 (abs)].
2 Supported by DK08828 awarded to T. Kalogeris, NIH DK32288 awarded to P. Tso, and a grant from the Proctor and Gamble Company.
3 The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.
4 Present address: Dept. of Surgery, LSU Medical Center, Shreveport, LA 71130.
5 To whom correspondence should be addressed.
Manuscript received 18 March 1996. Revision accepted 11 July 1996.