LIPID-METABOLISM IN THE LIVER STUDIED IN-VIVO WITH 2 ISOMERS OF LABELED FATTY-ACID ANALOGS

The two radioiodinated fatty acid analogs 15-(para-I-131-phenylpentade canoic acid (pPPA) and 15-(ortho-I-131-phenyl)-pentadecanoic acid (oPP A) are isomers with individually different routes in lipid metabolism but with near equal transport kinetics into tissue. Methods: Normal ad ult male Wistar rats (n = 79) and those with liver cell damage from ad riamycin treatment (n = 84) received 1.48 - 1.85 MBq I-131-pPPA or I-1 31-oPPA (specific activity, 33.3 - 46.3 GBq/mu M) into the jugular vei n. At 1, 2, 3, 5, 7, 10 and 20 min, livers of up to five animals per g roup were examined for total tracer uptake and tracer incorporation in to various lipid fractions. Results: Uptake of both isomers into the t otal liver plateaued at about 2 min; the ratio oPPA/pPPA in normal liv er averaged 2.63 and was significantly higher than the average ratio o f 1.50 after adriamycin treatment. This fall in ratio was mainly due t o an increase of pPPA uptake. Significant differences of the respectiv e ratios were found in the plateau for the phospholipids (9.7 versus 3 .0), cholesterol (2.4 versus 0.7) and triglycerides (2.0 versus 0.4). Conclusion: The dual-tracer technique with pPPA and oPPA promises to b e clinically useful for the diagnosis of liver disease by imaging the ratios of tracer uptake in the total liver and by in vitro analysis of the uptake ratio in serum triglycerides.