Journal of Lipid Research, Vol. 19, 1038-1046, November 1978
Copyright © 1978 by Lipid Research, Inc.

Origin and transport of the A-I and arginine-rich apolipoproteins in mesenteric lymph of rats

Katsumi Imaizumi , Richard J. Havel , Menahem Fainaru , and Jean-Louis Vigne

Cardiovascular Research Institute and Department of Medicine, University of California, San Francisco, CA 94143

Transport of apolipoprotein A-I and argininerich apolipoprotein in mesenteric lymph was examined in rats given constant intraduodenal infusions of saline, glucose in saline, or emulsified fat. Lymph flow in all groups was constant from 5 to 50 hr after beginning the infusions. Lymphatic transport of triglycerides was about 20-fold greater and transport of apoprotein A-I was about twofold greater in fat-infused rats than in the other two groups. In each group transport of apoprotein A-I bore a significant positive relationship to transport of triglycerides. Lymphatic transport of the arginine-rich apoprotein was only 6-12% of that of apoprotein A-I and was more closely related to lymphatic transport of total protein than to that of triglycerides. In fat-infused rats given [³H]lysine intraduodenally, about two-thirds of the ³H in the chylomicron proteins was in apoprotein A-I and only about 1% was in the arginine-rich apoprotein. Estimated specific activity of chylomicron proteins was highest for apoprotein A-I and apoprotein A-IV, and lowest for the arginine-rich apoprotein and proteins of low molecular weight (mainly C apoproteins). In fat-infused rats given constant intravenous infusions of radioiodinated high density lipoproteins from blood plasma, the specific activity of apoprotein A-I in lymph chylomicrons was only about 5% of that of apoprotein A-I in blood high density lipoproteins, indicating that more than 90% of the apoprotein A-I in chylomicrons was synthesized in the intestine. From these and other data it is concluded that both the intestine and liver are significant sources of apoprotein A-I whereas only the liver synthesizes significant amounts of the arginine-rich apoprotein.

Supplementary key words intestine • chylomicrons • high density lipoproteins • apolipoprotein A-IV • apolipoprotein C • apolipoprotein synthesis

Submitted on January 18, 1978
Accepted on May 5, 1978

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