Endocrine Abstracts

This study examined the action of GH on secretory activity and apoptosis (A) in porcine ovarian granulosa cells, as well as the role of protein kinase A (PKA), mitogen-activated protein kinase (MAPK), tyrosine kinase (TK), protein kinase G (PKG) and cyclin-dependent cdc2/p34 kinase in the mediation of its actions. The effects of exogenous pGH, with or without blockers of PKA (KT5720, Rp-cAMPS), MAPK (PD98059), TK (genistein, lavendustin), PKG (Rp-Br-PET-cGMPS, KT5823) and cdc2/P34 (olomoucine), were investigated in cultured cells by examining the secretion or expression of IGF-I, IGFBP-3, oxytocin (OT), prostaglandins F alpha (PGF) and E (PGE), PKA, MAPK/ERK1 and 2, CREB and A. Techniques included RIA, Western immunoblotting, immunocytochemistry and TUNEL.

GH addition significantly stimulated PKA and MAPK, but not CREB. Secretion of IGF-I and PGF were increased, secretion of IGFBP-3 and OT were decreased and PGE was unaffected. The incidence of A was lower. PKA blockers, given alone, decreased IGFBP-3 and OT output and increased PGF accumulation. They also prevented the effects of GH on IGF-I, PGF, IGFBP-3, OT and A. The MAP kinase blocker did not affect PGF, PGE and OT secretion but prevented or reversed the effects of GH on PGF and A. Neither the TK nor the cdc2/P34 blocker significantly affected A but the PKG blockers significantly increased it. TK and PKG blockers, prevented or reversed the inhibitory effect of GH on A, whilst the cdc2 blocker promoted it.

These observations demonstrate the involvement of GH, PKA- and MAPK-dependent intracellular mechanisms in the control of secretory functions and A in ovarian cells, and show that control of A operates through TK-, PKG- and cdc2/p34-dependent pathways. Furthermore, they suggest that GH can affect ovarian cells through the PKA-, MAPK-, TK-, PKG- and cdc2/p34-dependent signalling cascade.