Experimental and clinical studies on 131I-triolein absorption test:The necessity of purification of commercial 131I-triolein

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The purpose of this study is to reevaluate 131I-triolein test.1) Basic experimentsTen commercial 131I-triolein products were analyzed with thin layer chromatography by Stahle's method. Radioactivity of each fraction was found as follows; 10.9±6.8% in PL, 10.6±7.3% in Ch, 20.3±11.4% in FFA, 57.5±12.9% in TG and 0.7±1.0% in ChE fraction. From above results, commercial products appeared to be impure. Only triglyceride fraction of commercial 131I-triolein developed by above mentioned methods was extracted and named purified (radioiodinated) triolein.2) Animal experiments25 adult male dogs were fasted overnight and cannules were placed in thoracic duct, portal vein and femoral vein of dogs. Radioiodinated triolein (commercial or purified) mixed with cold meal of peanut oil was administered into the stomach or duodenum. Absorption tests without thoracic duct fistula, or with administration of 14C-triolein were performed as control. In the case of commercial triolein, the radioactivity appeared in portal blood as well as thoracic duct lymph. In the case of purified triolein administration, however, radioactivity appeared only in thoracic duct lymph and γ-ray of portal blood was negligible. So was in the case of 14C-triolein absorption tests. When thoracic duct lymph treated by 10% TCA solutions, precipitated radioactivity ratio was 90.4±6.3% in commercial triolein and 97.4±3.9% in purified triolein. By TLC method, radioactivity of thoracic duct lymph lipids existed 76.7±8.1% in the fraction of TG in commercial triolein and 86.8±3.9% in purified. In portal plasma lipids, 40% of radioactivity was found in PL fraction in the case of commercial triolein, but no γ-ray was found in all fraction in the purified triolein tests. This results means the same biochemical mechanism of absorption of purified 131I-triolein with 14C-triolein. When chylomicron composed of 131I-triolein transported into systemic blood circulation, chylomicron was metabolized and large amounts of isolated inorganic 131I appeared in blood.3) Clinical investigations75 commercial and 35 purified radioiodinated triolein tests were performed on hospitalized patients. Fecal excretion rate using purified 131I-triolein corresponded more to that of chemical fat balance study than the results obtained by use of commercial 131I-triolein. Only from 30 to 50% of radioactivity of the venous blood was precipitated by TCA in both cases of commercial and purified triolein administration. Radioactivity of lipids in the plasma extracted after Folch's method was evaluated in each fraction by TLC. Much radioactivity in the plasma existed in the fraction of FFA instead of TG which contained high radioactivity ratio in thoracic duct lymph. From above findings, it is not proper to speculate fecal excretion rate of 131I-triolein on the basis of radioactivity levels of blood, which are effected by the metabolism of lipids as well as absorption.
財団法人日本消化器病学会の論文

Experimental and clinical studies on 131I-triolein absorption test:The necessity of purification of commercial 131I-triolein

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