Arachidonic acid metabolism in isolated pancreatic islets. V. The enantiomeric composition of 12-hydroxy-5,8,10,14-eicosatetraenoic acid indicates synthesis by a 12-lipoxygenase rather than a monooxygenase.
Recent evidence indicates that the arachidonate metabolite 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) or its precursor may act as a second messenger in stimulus-response coupling in a variety of cells including Aplysia neurons, adrenal glomerulosa cells, and pancreatic islets. The compound 12(S)-HETE is generated from the precursor 12(S)-hydroperoxy-5,8,10,14-eicosatetraenoic acid (12(S)-HPETE), which is a product of the 12-lipoxygenase enzyme. Some cells have recently been found to produce the enantiomer 12(R)-HETE, apparently via a cytochrome P-450 monooxygenase, and the biologic actions of 12(R)-HETE and 12(S)-HETE differ. We have examined the stereochemistry of 12-HETE from isolated pancreatic islets both radiochemically and by a new mass spectrometric method capable of quantitating subnanogram amounts of 12-HETE stereoisomers. Endogenous 12-HETE from islets was found to be exclusively the S-isomer. D-Glucose stimulated both insulin secretion and islet accumulation of 12(S)-HETE but not of 12(R)-HETE. Pharmacologic inhibition of islet 12-HETE biosynthesis also suppressed glucose-induced insulin secretion. These findings suggest that islet 12-HETE is a product of a 12-lipoxygenase rather than of a cytochrome P-450 monooxygenase and further implicate 12-lipoxygenase products in stimulus-secretion coupling.
Turk
J
J
Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110.
Wolf
B A
BA
Easom
R A
RA
Hughes
J H
JH
McDaniel
M L
ML
D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; D000818:Animals; D001092:Arachidonate 12-Lipoxygenase / Q000378:metabolism*; D001091:Arachidonate Lipoxygenases / Q000378:metabolism*; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D005947:Glucose / Q000494:pharmacology; D006893:Hydroxyeicosatetraenoic Acids / Q000378:metabolism; D007515:Islets of Langerhans / Q000378:metabolism*; D051381:Rats; D013237:Stereoisomerism
D001095:Arachidonic Acids; D006893:Hydroxyeicosatetraenoic Acids; D016718:Arachidonic Acid; D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; D001091:Arachidonate Lipoxygenases; D001092:Arachidonate 12-Lipoxygenase; D005947:Glucose