Arachidonate metabolism in macrophages is affected by albumin.
The incorporation of externally added arachidonic acid into membrane lipids of cultured liver macrophages was found to be strongly inhibited by albumin. Furthermore this protein increased the appearance of radiolabelled arachidonic acid in cell media from [3H] arachidonic acid-prelabelled cells but inhibited almost totally the stimulus-induced formation of prostanoids. Analysis of the membrane lipids revealed that in the presence of albumin arachidonic acid was released to almost the same percentage from all phospholipids, independently of the stimulus. In contrast, in the absence of albumin a significant loss of arachidonic acid was observed for phosphatidylcholine and phosphatidyl-inositol only and the degree of the decrease in label was dependent on the stimulus. Although the exact mechanisms for these actions of albumin are not yet known this protein clearly exerts an inhibitory effect on arachidonic acid incorporation into membrane lipids as well as on the synthesis of different eicosanoids in macrophages; on the other hand albumin leads to an enhanced appearance of arachidonic acid in the cell media. Therefore this protein may be able to control the level of free arachidonic acid within and outside the cell and thereby the conversion of arachidonic acid into eicosanoids.
Dieter
P
P
Biochemisches Institut, Universität Freiburg im Breisgan, Federal Republic of Germany.
Krause
H
H
Schulze-Specking
A
A
D000418:Albumins / Q000494:pharmacology*; D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism*; D002417:Cattle; D003470:Culture Media; D015777:Eicosanoids / Q000096:biosynthesis; D005459:Fluorides / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D007728:Kupffer Cells / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism*; D008297:Male; D008563:Membrane Lipids / Q000378:metabolism; D010703:Phorbol Esters / Q000494:pharmacology; D010743:Phospholipids / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D014316:Tritium; D015054:Zymosan / Q000494:pharmacology
D000418:Albumins; D001095:Arachidonic Acids; D003470:Culture Media; D015777:Eicosanoids; D007476:Ionophores; D008563:Membrane Lipids; D010703:Phorbol Esters; D010743:Phospholipids; D014316:Tritium; D016718:Arachidonic Acid; D015054:Zymosan; D005459:Fluorides