Arachidonate released upon agonist stimulation preferentially originates from arachidonate most recently incorporated into nuclear membrane phospholipids.

摘要: When icosanoid-producing cells are stimulated by an agonist, 2-10% of total cellular arachidonate is released from phospholipids, and a variable percentage the subsequently converted into icosanoids. We used mouse fibrosarcoma cell line (HSDM1C1) which synthesizes prostaglandin E2 in response to bradykinin stimulation address following questions: 1) upon newly incorporated preferentially phospholipids over previously 2) there corresponding change phospholipid or membrane compartmentation explain preferential release arachidonate? To study changes availability for we incubated HSDM1C1 with 0.67 microM [14C]arachidonate 15 min chased pulse radiolabeled normal serum fatty acids. found that during 15-min pulse, percent decreased nearly 3-fold 8.9 +/- 0.5% at 5 chase 3.6 0.2% (mean S.E., n = 6, P less than 0.001) after only 60 chase. Percent nonpulsed controls was 3-4%. Although significantly chase, always originated predominantly phosphatidylinositol. There no decrease activities enzymes required this time period. also observed throughout period remained esterified same class it initially (approximately 40% diacyl phosphatidylcholine, phosphatidylinositol, 15% phosphatidylethanolamine. In fractionation experiments, 1-3 h subcellular fractions containing nuclei, as became progressively unavailable phospholipids. Thus, our results indicate stimulation, most recently pool arachidonate, high concentration nuclear membrane, rapidly moves out releasable while remaining moiety incorporated. This indicates has marked influence on metabolism arachidonate.