ARACHIDONIC-ACID AND LIPOXYGENASE PRODUCTS STIMULATE PROTEIN-KINASE CB MESSENGER-RNA LEVELS IN PITUITARY ALPHA-T3-1 CELL-LINE - ROLE IN GONADOTROPIN-RELEASING-HORMONE ACTION
Z. Shragalevine et al., ARACHIDONIC-ACID AND LIPOXYGENASE PRODUCTS STIMULATE PROTEIN-KINASE CB MESSENGER-RNA LEVELS IN PITUITARY ALPHA-T3-1 CELL-LINE - ROLE IN GONADOTROPIN-RELEASING-HORMONE ACTION, Biochemical journal, 316, 1996, pp. 667-670
The cross-talk of arachidonic acid (AA) and its lipoxygenase products
with protein kinase C beta (PKC beta) mRNA levels during the action of
gonadotropin-releasing hormone (GnRH) was investigated in the pituita
ry alpha T3-1 cell line. The addition of AA or its 5-lipoxygenase prod
ucts 5-hydroxyeicosatetraenoic acid (5-HETE) or leukotriene C-4 (LTC(4
)) for 30 or 60 min stimulated PCK beta, but not PKC alpha mRNA levels
(3-5-fold); PCK gamma is not expressed by the cells. Other HETEs or l
eukotrienes tested showed no significant effect. The range of effectiv
e concentration for LTC(4) and 5-HETE (around 10(-10) M) is the range
found in GnRH-stimulated pituitary cells. Although PKC beta mRNA level
s were preferentially elevated by LTC(4) and 5-HETE at early time poin
ts, PKC alpha mRNA levels were elevated at 6-12 h of incubation when P
KC beta mRNA levels returned to basal levels. The addition of the phos
pholipase A(2) inhibitor 4-bromophenacyl bromide or the selective 5-li
poxygenase inhibitor L-656,224 abolished [D-Trp(6)]GnRH (GnRH-A) eleva
tion of PKC beta mRNA levels, whereas PKC alpha mRNA levels were not i
ncreased by this neuro-hormone. The cyclo-oxygenase inhibitor indometh
acin elevated basal PKC beta mRNA levels and potentiated the GnRH-A re
sponse. Cross-talk exists between AA and some of its lipoxygenase prod
ucts and PKC beta gene expression during eel signalling. AA, 5-HETE an
d LTC(4) participate in the rapid stimulation of PKC beta mRNA levels
by GnRH.