Intestinal versus hepatic contribution to circulating triglyceride levels

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Abstract
Using intravenous injected [2‐3H] glycerol, measurements wee made of the kinetics of appearance and disappearance of circulating [3H] labeled triglyceride in rats fed a fat free diet containing either no orotic acid (controls) or 2% orotic acid. Following injection of [3H] glycerol, more time is required for the initial appearance of [3H] triglyceride in the circulation of orotic acid treated rats than controls. The sustained entry of triglyceride into the circulation of orotic acid fed rats was only one‐half times as rapid as that seen for control rats. Ca. 10% as much [3H] triglyceride entered the circulation of the orotic acid treated rats as compared with controls. However, the clearance of [3H] triglyceride from the circulation of the orotic acid fed rat was only ca. one‐half times as rapid as that of the control rat. This apparently is due to differences between the lipoproteins produced by the intestines and liver, rather than to changes in the ability of the orotic acid fed animal to clear lipoprotein‐triglyceride from the circulation. Labeled lipoproteins taken from controls and injected into orotic acid treated rats were cleared from the circulation more than twice as rapidly as those taken from orotic acid fed rats and injected into controls. Considering the measured levels of plasma triglyceride synthesis and the slower turnover of the triglycerides produced by the orotic acid fed rat, the findings of this study indicate that the intestines supply 20% or more of the total plasma triglyceride in the absence of dietary fat.