Open AccessPreferential Esterification of Endogenously Formed 5‐Hydroxyeicosatetraenoic Acid to Phospholipids in Activated Polymorphonuclear Leukocytes
Author(s) -
Arai Masayoshi,
Imai Hirotaka,
Metori Atsuko,
Nakagawa Yasuhito
Publication year - 1997
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1997.00513.x
Subject(s) - hydroxyeicosatetraenoic acid , endogeny , incubation , chemistry , biochemistry , stimulation , arachidonic acid , biosynthesis , biology , endocrinology , enzyme
The esterification of endogenously formed 5‐hydroxyeicosatetraenoic acid (5‐HETE) to cellular lipids in rat polymorphonuclear leukocytes (PMNL) was studied quantitatively by a fluorometric method using HPLC. Rapid and maximal production of free 5‐HETE was observed after a 5‐min stimulation of PMNL with A23187. The amount of free 5‐HETE then declined rapidly, while that of 5‐HETE esterified to phospholipids and triacylglycerol concomitantly increased in a time‐dependent manner. Stimulation by A23187 yielded approximately 100 ng/10 7 cells esterified 5‐HETE in 60 min, which corresponded to the decrease in the amount of free 5‐HETE from 5 min to 60 min and indicated that free 5‐HETE, which was formed endogenously, was metabolized predominantly by esterification to cellular lipids. The esterification profile of exogenous 5‐HETE was different from that of endogenous 5‐HETE. 5‐[ 3 H]HETE, which was added exogenously to the culture medium, was rapidly incorporated into PMNL and almost 80% of the total radioactivity was located in triacylglycerol. A quantitative study revealed that endogenous 5‐HETE was esterified equally to phospholipids and triacylglycerol. Like PMNL, peritoneal macrophages treated with A23187 released significant amounts of 5‐HETE. However, less 5‐HETE was esterified to cellular lipids than in PMNL. Negligible amounts of 12‐HETE, produced by activated peritoneal macrophages or activated platelets after a challenge with A23187, were esterified during the entire incubation. Exogenous 5‐HETE was rapidly taken up by PMNL, but was incorporated into macrophages much more slowly than into PMNL. No uptake of 12‐HETE into macrophages was observed. The rapid uptake of exogenous 5‐HETE was strongly inhibited by the suppression of acylation of 5‐HETE by triacsin C. These results suggest that esterification might be one of the factors that regulate the rate of incorporation of 5‐HETE.