Mass spectrometric characterization of arachidonate-containing plasmalogens in human pancreatic islets and in rat islet .beta.-cells and subcellular membranes

作者：Sasanka Ramanadham, Alan Bohrer, Richard W. Gross, JOHN W. TURK · 发表于：Biochemistry · 年份：1993 · DOI：10.1021/bi00212a015 · 被引用次数：61 · 研究领域：Pancreatic function and diabetes、Diet, Metabolism, and Disease、Cannabis and Cannabinoid Research

Pancreatic islets, when stimulated with D-glucose, secrete insulin by processes requiring glycolytic metabolism and generation of ATP. Hydrolysis of membrane phospholipids also occurs in glucose-stimulated islets, resulting in accumulation of nonesterified arachidonate, which facilitates Ca2+ entry and the rise in beta-cell [Ca2+] that triggers insulin secretion. Glucose-induced hydrolysis of arachidonate from islet phospholipids is mediated in part by an ATP-stimulated, Ca(2+)-independent (ASCI) phospholipase A2 (PLA2) which prefers plasmenyl over diacyl phospholipid substrates. Here we characterize the endogenous plasmalogen content of islet cells and subcellular membranes. Fast atom bombardment mass spectrometric analyses demonstrated that three of the most abundant molecular species of ethanolamine phospholipids in rat pancreatic islets were plasmalogens with sn-2 arachidonate residues and palmitic, oleic, or stearic aldehyde residues, respectively, in the sn-1 position. Purified populations of beta-cells prepared by fluorescence-activated cell sorting were also found to contain these plasmenylethanolamine molecular species in abundance similar to that in intact islets and greater than that in islet alpha-cells. Both islet plasma membranes (PM) and endoplasmic reticulum (ER) also contained these plasmenylethanolamine species, which accounted for 42% (PM) to 64% (ER) of the ethanolamine phospholipid arachidonate content of these membranes, as measured by stable isotope dil...