SYNTHESIS OF MONOHYDROXYLATED FATTY-ACIDS FROM LINOLEIC-ACID BY RAT AORTIC SMOOTH-MUSCLE CELLS AND TISSUES - INFLUENCE ON PROSTACYCLIN PRODUCTION

We have investigated whether cellular metabolism of linoleic acid (18: 2) can influence prostacyclin (PGI2) production by cultured rat aortic smooth muscle cells (SMC) and tissues. Incubation of rat SMC homogena tes with [1-C-14]18:2 results in the enzymatic synthesis of [C-14]13-H ODE (hydroxyoctadecadienoic acid) and to a lesser extent [C-14]9-HODE as defined by gas-liquid chromatography-mass spectrometry (GLC-MS). Th e observed changes, in percent enzymatically synthesized 13-HODE in th e presence of indomethacin, aspirin, metyrapone, 15-HPETE (hydroperoxy eicosatetraenoic acid), and NDGA, suggest that it is formed from the P GH (prostaglandin endoperoxide) synthase pathway. Incubation of intact adherent SMC with [C-14]linoleic acid demonstrates that the monohydro xylated compounds are predominantly esterified within the membrane pho spholipids and not released into the incubation medium. The simultaneo us incubation or a short-term preincubation of 18:2 and arachidonic ac id (20:4) do not modify the enzymatic profile of 20:4 transformation. By contrast, long-term preincubation of cells with 18:2 or 13-HODE sti mulates the transformation of exogenously added [C-14]20:4 to [C-14]6- keto PGF1alpha. However, exogenous 13-HODE does not enhance [C-14]6-ke to PGF1alpha recovery from [C-14]20:4 prelabeled SMCs. Our results dem onstrate that 18:2 is a substrate for PGH-synthase in rat aortic SMC a nd tissues. The 13-HODE formed is essentially esterified in cell phosp holipids and remains without any significant effects on the release of [C-14]6-keto PGF1alpha from [C-14]20:4 prelabeled SMC.