UPTAKE, DISTRIBUTION AND RELEASE OF H-3 ARACHIDONIC-ACID FROM HUMAN ENDOMETRIUM

The lysophosphatide acyltransferase blocking agent ethylmercurisalicylate (merthiolate) was used to investigate the uptake and release of arachidonic acid from explants of human endometrium in short term tissue culture. Tissue explants were (a) incubated with 3H-arachidonic acid for 1-24 h in the presence or absence of 0.5-50 μM merthiolate, and (b) prelabelled with 3H-arachidonic acid for 18 h followed by incubation with or without 50 μM merthiolate for 1-24 h. Neutral lipids, phospholipids and arachidonic acid were separated by thin layer chromatography and uptake and release of 3H-arachidonic acid expressed as % total uptake. The triglyceride pool was the main target for arachidonic acid uptake. Incorporation increased from 9.1% at 1 h to 56.6% at 24 h. Uptake into phospholipids increased from 8.1% at 1 h to 19.6% at 24 h with phosphatidylcholine accounting for 3.8% and 8.8% respectively. Incubation with 50 μM merthiolate rapidly reduced uptake into triglycerides (to 1.8% at 1 h and 0.9% at 24 h), whereas the effect on uptake into phospholipids (5.9% at 1 h, 3.4% at 24 h) was much less marked. There was a dose related inhibition of arachidonic acid incorporation into both triglycerides and phospholipids, but a lower dose of merthiolate (1 μM) was required to reduce uptake into triglycerides than into phospholipids (5 μM). Uptake into mono- and diglycerides was low and unaffected by merthiolate. Incubation of prelabelled tissue with 50 μM merhiolate resulted in a 20% increase in the release of arachidonic acid from triglycerides and a corresponding accumulation of labelled monoglyceride. There was a small but significant decrease in 3H-phosphatidylethanolamine content. These findings suggest that, in endometrium, the triglyceride pool may be a more important source of free arachidonic acid than hitherto considered. © 1990.