Thrombin-stimulated increases in cytosolic Ca2+ level and gonadotropin-releasing hormone release in GT1-7 neurons.
The effects of thrombin on cytosolic calcium levels ([Ca2+]cyt), and on gonadotropin-releasing hormone (GnRH) release, were characterized in cultured GT1-7 neurons. GnRH release from GT1-7 neurons was pulsatile with an average pulse amplitude of 14.3+/-5.8 pg x min x ml(-1) and an average pulse duration of 21.3+/-4.2 min. The [Ca2+]cyt response to 0.005 to 0.2 U/ml thrombin was saturable and concentration dependent (EC50 = 0.0268 U/ml). Ethyleneglycotetraacetic acid (EGTA) chelation of extracellular Ca2+ resulted in an approximately 70% attenuation of thrombin-stimulated increase in [Ca2+]cyt. By use of a special superfusion system, a 5-min exposure to 0.1 U/ml thrombin significantly increased the amplitude (193.2+/-67.8 pg x min x ml(-1); P = 0.001) but not the duration (22.5+/-2.4 min; P = 0.8) of GnRH release. These results suggest that thrombin increases [Ca2+]cyt and GnRH release from GT1-7 neurons via specific membrane-bound receptors.
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Department of Obstetrics and Gynecology, The University of Texas Health Science Center, San Antonio 78284, USA. chene@uthscsa.edu
King
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Chang
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Norris
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Schenken
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D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002614:Chelating Agents / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D051379:Mice; D009474:Neurons / Q000187:drug effects* / Q000502:physiology*; D010741:Phospholipases A / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology*
D002614:Chelating Agents; D016718:Arachidonic Acid; D007987:Gonadotropin-Releasing Hormone; D004533:Egtazic Acid; D010741:Phospholipases A; D013917:Thrombin; D002118:Calcium