Synthesis of 12(R)- and 12(S)-hydroxyeicosatetraenoic acid by porcine ocular tissues

J Ocul Pharmacol. Fall 1994;10(3):525-35. doi: 10.1089/jop.1994.10.525.

Abstract

Microsomal fractions from porcine ocular tissues synthesized 12(S)-5,8,10,14-hydroxyeicosatetraenoic acid [12(S)-HETE] from arachidonic acid by a membrane-bound lipoxygenase and 12(R)-HETE by the cytochrome P450-dependent monooxygenase system. Both activities were the highest in corneal microsomes. The 12(R)-HETE synthesizing activity of corneal microsomes was dependent on NADPH and inhibited by 0.1 mM SKF-525A, an inhibitor of P450 enzymes. The activity to form 12(R)-enantiomer was significantly enhanced by treatment of corneal epithelium with 3-methylcholanthrene or clofibrate. The induced activity was suppressed by cycloheximide, indicating that the induction of enzyme activities involved a translational process. The effect of these inducers on 12(R)-HETE synthesizing activity appeared to be additive. The activity to form 12(S)-enantiomer was markedly stimulated by 3 mM CaCl2. The 12-lipoxygenase of corneal microsomes was capable of oxygenating linoleic acid in addition to arachidonic acid, a characteristic of 12-lipoxygenases of the leukocyte type. 12(R)-HETE at 10(-6) M inhibited almost completely the Na,K-ATPase of corneal epithelium but had little or no effect on ciliary epithelial enzymic activity. 12(S)-HETE at 10(-6) M also inhibited corneal enzymic activity but to a lesser extent, and had no significant effect on ciliary epithelial Na,K-ATPase activity.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid
  • Animals
  • Anterior Eye Segment / metabolism
  • Arachidonate 12-Lipoxygenase / metabolism
  • Arachidonic Acid / metabolism
  • Chromatography, High Pressure Liquid
  • Cytochrome P-450 Enzyme System / metabolism
  • Eye / metabolism*
  • Hydroxyeicosatetraenoic Acids / biosynthesis*
  • Hydroxyeicosatetraenoic Acids / pharmacology
  • Microsomes / metabolism
  • Retina / metabolism
  • Sodium-Potassium-Exchanging ATPase / antagonists & inhibitors
  • Sodium-Potassium-Exchanging ATPase / metabolism
  • Stereoisomerism
  • Swine

Substances

  • Hydroxyeicosatetraenoic Acids
  • Arachidonic Acid
  • 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid
  • Cytochrome P-450 Enzyme System
  • Arachidonate 12-Lipoxygenase
  • Sodium-Potassium-Exchanging ATPase