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 homogenates with [1-14C]18:2 results in the enzymatic synthesis of [14C]13-HODE (hydroxyoctadecadienoic acid) and to a lesser extent [14C]9-HODE as defined by gas-liquid chromatography-mass spectrometry (GLC-MS). The observed changes, in percent enzymatically synthesized 13-HODE in the presence of indomethacin, aspirin, metyrapone, 15-HPETE (hydroperoxyeicosatetraenoic acid), and NDGA, suggest that it is formed from the PGH (prostaglandin endoperoxide) synthase pathway. Incubation of intact adherent SMC with [14C]linoleic acid demonstrates that the monohydroxylated compounds are predominantly esterified within the membrane phospholipids and not released into the incubation medium. The simultaneous incubation or a short-term preincubation of 18:2 and arachidonic acid (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 stimulates the transformation of exogenously added [14C]20:4 to [14C]6-keto PGF1 alpha. However, exogenous 13-HODE does not enhance [14C]6-keto PGF1 alpha recovery from [14C]20:4 prelabeled SMCs. Our results demonstrate that 18:2 is a substrate for PGH-synthase in rat aortic SMC and tissues. The 13-HODE formed is essentially esterified in cell phospholipids and remains without any significant effects on the release of [14C]6-keto PGF1 alpha from [14C]20:4 prelabeled SMC.