IDENTIFICATION OF ENDOGENOUS 5S,12S-DIHYDROXY-6,8,10,14-(E,Z,E,Z)-EICOSATETRAENOIC ACID (5S,12S-DIHETE) IN CHICK OSTEOBLASTS AND EPIPHYSEAL CARTILAGE

Cell homogenates were obtained from chick osteoblast-like cells and epiphyseal growth plates. The lipid fraction was extracted with ethyl acetate and separated by RP-phase HPLC. Reverse-phase HPLC analysis of this fraction showed a major peak displayed a conjugated tetraene structure and this endogenous synthetic compound could be partially blocked by heat treatment at 100-degrees-C for 5 min. After methylation, this peak was further purified by SP-HPLC and a major peak was identified by an U.V. absorption at lambda(max) of 271 nm and shoulders at 261 and 281 nm. The compound was hypothetically proposed by gas chromatography and mass spectrometry (GC/MS) as the cyclohexadiene derivative of 5S,12S-dihydroxy-6,8,10,14-(E,Z,E,Z)-eicosatetraenoic acid (5S,12S-diHETE) with a ring closure at C6 and C11. These results demonstrated that the 5S,12S-diHETE is an endogenous eicosanoid in both intramembranous and endochondral skeletal tissues.