arachidonic acid by either phospholipase A2 or phospholipase
C is a rate-limiting step in prostaglandin synthesis
(Irvine, 1982; Lapetina, 1982). The composition of cellular
phospholipids is related to the dietary lipid intake and thus
will play an important role in determining both the amount
and type of prostaglandins produced. Although LA and LNA
can both act as precursors for prostaglandin synthesis, high
amounts of precursor can also reduce both arachidonic
acid generation and prostaglandin synthesis via inhibition
of phospholipase A2 and cyclo-oxygenase (Thatcher et al.,
1995). Arachidonic acid has also been implicated in the
acute regulation of steroid synthesis. Trophic hormoneinduced
steroid synthesis requires increased expression
of steroidogenic acute regulatory protein (StAR), which
mediates transfer of cholesterol from the cytosol to the inner
mitochondrial membrane (Stocco and Clark, 1996).
Arachidonic acid increases the expression of StAR (Wang
and Stocco, 1999).