Smith C E, Wakefield I, King J A, Naor Z, Millar R P, Davidson J S
Department of Chemical Pathology, UCT Medical School, Cape Town, Republic of South Africa.
FEBS Lett. 1987 Dec 10;225(1-2):247-50. doi: 10.1016/0014-5793(87)81167-5.
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.
