Protein-facilitated export of arachidonic acid from pig neutrophils.
Activated neutrophils release a variety of eicosanoids into the extracellular medium including arachidonic acid, 5-hydroxyicosatetraenoic acid, and leukotriene A4 and B4. In this study, the mechanism of arachidonic acid export has been examined using inside-out plasma membrane vesicles from pig polymorphonuclear leukocytes. Tritiated arachidonic acid associated rapidly with the membrane vesicles and crossed the membrane into the intravesicular space in a time-dependent and saturable manner. Half the maximal influx rate was measured at an arachidonate concentration of 5.7 microM, and a maximal influx velocity of 3.0 nmol/mg x min was determined at pH 6.8. Influx into vesicles was sensitive to a number of common anion transport inhibitors including pentachlorophenol, phloretin, diiodosalicylic acid, and quercetin as well as to the proteases trypsin and Pronase, suggesting a protein-dependent process. Furthermore, influx was temperature-sensitive with an energy of activation of 11.6 kcal/mol. Varying extravesicular concentration of ATP, Na+, or K+ had no impact on arachidonate influx, whereas changes in pH had a profound effect; optimum transport activity was observed at an extravesicular pH of 6, whereas raising the pH to 9.5 essentially abolished uptake. These results indicate and initially characterize a novel protein-facilitated arachidonate export mechanism in pig neutrophils.
Krischer
S M
SM
Institute of Pharmaceutical Biology, University of Munich, Karlstrasse 29, D-80333 Munich, Federal Republic of Germany.
Eisenmann
M
M
Bock
A
A
Mueller
M J
MJ
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000097:blood*; D002151:Calorimetry; D002458:Cell Fractionation; D005033:Ethylmaleimide / Q000494:pharmacology; D006893:Hydroxyeicosatetraenoic Acids / Q000097:blood; D066298:In Vitro Techniques; D007700:Kinetics; D017572:Leukotriene A4 / Q000097:blood; D007975:Leukotriene B4 / Q000097:blood; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D010587:Phagocytosis; D010588:Phagosomes / Q000378:metabolism* / Q000648:ultrastructure; D010693:Phloretin / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011794:Quercetin / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D013552:Swine; D013696:Temperature
D006893:Hydroxyeicosatetraenoic Acids; D017572:Leukotriene A4; D007975:Leukotriene B4; D016718:Arachidonic Acid; C022022:5-hydroxy-6,8,11,14-eicosatetraenoic acid; D000255:Adenosine Triphosphate; D011794:Quercetin; D012964:Sodium; D005033:Ethylmaleimide; D011188:Potassium; D010693:Phloretin