Extracellular Signal-Regulated Kinase (ERK) Activation and Mitogen-Activated Protein Kinase Phosphatase 1 Induction by Pulsatile Gonadotropin-Releasing Hormone in Pituitary Gonadotrophs
Figure 2
Schematic pattern of ERK activation by perifused GnRH stimulation. (a) When cells were exposed to continuous GnRH in perifused conditions, ERK activation was significantly increased, after 10 min, and increased ERK phosphorylation was sustained and gradually decreased to the basal. (b) At high frequency of GnRH pulse stimulation (one pulse very 30 min), ERK phosphorylation increased to a maximum at 10 min, and then levels rapidly decreased to bas line levels within 30 min. A similar pattern of ERK phosphorylation was observed in response to subsequent pulse of GnRH. (c) At a slower frequency of GnRH pulse stimulation (one pulse every 2 h), ERK was more rapidly phosphorylated by GnRH pulse, and increase was more sustained, remaining elevated, and then slowly decreased to the baseline levels. A similar pattern of ERK phosphorylation was observed in response to subsequent pulse of GnRH.
