The initial phase of GnRH-stimulated LH release from pituitary cells is independent of calcium entry through voltage-gated channels.
Kinetic studies on gonadotropin-releasing hormone (GnRH)-stimulated luteinizing hormone (LH) release were undertaken using rat and chicken pituitary cell cultures. In response to continuous GnRH stimulation, a biphasic pattern of LH release was demonstrated. The two phases showed different susceptibility to the voltage-gated Ca2+ channel blockers D600 and nifedipine. The first (transient) phase of LH release was unaffected by the Ca2+ channel blockers whereas the second (sustained) phase was inhibited by both drugs. These results indicate that the initial phase of LH release is independent of Ca2+ entry through voltage-gated Ca2+ channels and may depend on mobilisation of intracellular Ca2+ or entry of extracellular Ca2+ through another mechanism.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D002645:Chickens; D005711:Gallopamil / Q000494:pharmacology; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D007986:Luteinizing Hormone / Q000378:metabolism*; D008297:Male; D009543:Nifedipine / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D051381:Rats
D007473:Ion Channels; D007987:Gonadotropin-Releasing Hormone; D005711:Gallopamil; D007986:Luteinizing Hormone; D009543:Nifedipine; D002118:Calcium