Protein kinase C inhibitors stimulate arachidonic and docosahexaenoic acids release from uterine stromal cells through a Ca2+-independent pathway

The mechanisms underlying arachidonic acid (AA) release by uterine stromal (U-III) cells were studied. Stimulation of AA release by calcium ionophore and PMA are inhibited by various PKC inhibitors and by calcium deprivation, These results suggest the involvement of an AA-specific cPLA(2) as the release of docosahexaenoic acid (DHA) from prelabelled cells is much lower than the release of AA, The results also show a more original stimulation of AA and DHA release induced by PKC inhibitors, which is insensitive to calcium deprivation, This stimulation is not due to acyltransferase inhibition, suggesting the participation of a Ca2+-independent PLA(2) (iPLA(2)), However, iPLA(2) activity measured in U-III cells is inhibited by the specific iPLA(2) inhibitor, EEL, and is not stimulated by PKC inhibitors, in contrast with the AA and DHA release. It seems therefore that this iPLA(2) cannot be involved in this mechanism, The participation of another iPLA(2), EEL-insensitive, is discussed. (C) 1998 Federation of European Biochemical Societies.