Dual modulation of K channels by thyrotropin-releasing hormone in clonal pituitary cells

摘要: Transmembrane electrical activity in pituitary tumor cells can be altered by substances that either stimulate or inhibit their secretory activity. Using patch recording techniques, we have measured the resting membrane potentials, action transmembrane macroscopic ionic currents, and single Ca2+-activated K channel currents of GH3 GH4/C1 rat response to thyrotropin-releasing hormone (TRH). TRH, which stimulates prolactin secretion, causes a transient hyperpolarization potential followed period elevated frequency. In voltage clamped internally dialyzed with solutions containing K+, TRH application results increase more protracted decrease voltage-dependent currents. However, K+-free solutions, produces no changes inward Ca2+ Ba2+ through Ca channels. The time courses effects on correlate phases hyperexcitability, respectively. During whole cells, increases cell-attached patches not directly exposed TRH. contrast, applied excised change behavior. We conclude (i) triggers intracellular release, opens channels, (ii) depresses channels during hyperexcitable phase, further Ca2+, (iii) does modulate