Gonadotropin-releasing hormone modulation of protein kinase-C activity in perifused anterior pituitary cell cultures.
The ability of GnRH to modulate protein kinase-C (PKC) activity was examined in perifused rat pituitary cell cultures. Under these conditions, LH release and GnRH receptor number remained unchanged after repeated pulses of 1 nM GnRM, whereas PKC (measured both enzymatically and by radioligand assay) showed an initial increase in kinase activity after the first pulse of GnRH (approximately 2-fold), followed by down-regulation of PKC activity with subsequent pulses of the releasing hormone. It was also observed that the GnRH-stimulated down-regulation of PKC was dependent on the presence of extracellular calcium, which was not the case for the initial up-regulation of PKC. These findings are consistent with a modulating role of the GnRH receptor on PKC activity through a Ca2(+)-dependent process. This study also provides further evidence that GnRH-stimulated LH release and PKC activity can be uncoupled.
Andrews
W V
WV
Department of Pharmacology, University of Iowa College of Medicine, Iowa City 52242-1109.
Hansen
J R
JR
Janovick
J A
JA
Conn
P M
PM
D000818:Animals; D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000502:physiology*; D010477:Perfusion / Q000379:methods; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000201:enzymology*; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D011966:Receptors, LHRH / Q000378:metabolism
D011966:Receptors, LHRH; D007987:Gonadotropin-Releasing Hormone; D011493:Protein Kinase C; D002118:Calcium