Absorption and metabolism of 1-14C-hydroxy octadecadienoate in the rat

The metabolism of 1-¹⁴C-9(13)-hydroxy octadecadienoic acid methyl ester (1-¹⁴C-HAME) by the rat was investigated in vivo and in liver slices. A 1.5 mg dose of 1-¹⁴C-HAME administered by stomach tube was efficiently hydrolyzed and absorbed from the intestinal tract. In comparison with 1-¹⁴C-methyl linoleate (1-¹⁴C-ML), 1-¹⁴C-HMAE was more extensively oxidized to¹⁴CO₂ in vivo and in vitro. After 1-¹⁴C-HAME administration as much as 50% of the radioactivity in the adipose tissue triglycerides was associated with¹⁴C-hydroxy fatty acids. The remaining activity was present in randomly labeled normal fatty acids. No evidence was obtained for the incorporation of¹⁴C-hydroxy acids into liver lipids; most of the radioactivity from 1-¹⁴C-HAME in this organ was recovered in saturated and monoenoic fatty acids. About 10% of the radioactivity 24 hr after 1-¹⁴C-HAME administration was associated with triglyceride trienoic acids, indicating that at least a portion of this acid was dehydrated in the liver. An unidentified polar acid was detected in the urine of the 1-¹⁴C-HAME-treated animals.