Abstract.
In clonal rat somatomammotroph cells (GH3/B6) Ca2+ influx through voltage-dependent Ca2+ channels is important for regulating the Ca2+ concentration that mediates hormone secretion. To study the Ca2+ channel subtypes in GH3/B6 cells, Ca2+ channel currents were recorded with the whole-cell configuration of the patch-clamp technique using Ba2+ as the charge carrier. Forty-nine percent of the total Ba2+ current amplitude was mediated by a nifedipine-sensitive current (L-type). In addition, three other high-voltage-activated Ca2+ channel current components could be distinguished pharmacologically: 10 nM ω-agatoxin-IVA-sensitive current (22%; P-type), ω-conotoxin-MVIIC-sensitive current (18%; Q-type), and toxin-resistant current (24%). Since ω-conotoxin GVIA (2 µM) had no blocking effect, N-type Ca2+ channels are assumed not to be present in GH3/B6 cells. The T-type Ca2+ channel current was either absent or very small. Different pore-forming α1 subunits of Ca2+ channels were found to be expressed in GH3/B6 cells, which could be the molecular correlates of the different Ba2+ current subtypes: α1G of T-type, α1C, α1D and α1S of L-type, and α1A of P/Q-type current. In addition, transcripts for β1, β2 and β3 subunits were detected. Blockage of L-type channels with 10 µM nifedipine or P/Q-type channels with 10 nM ω-agatoxin MVIIC + 200 nM ω-conotoxin blocked action potential firing in GH3/B6 cells and decreased basal prolactin secretion.
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Received after revision: 29 January 2001
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Glassmeier, .G., Hauber, .M., Wulfsen, .I. et al. Ca2+ channels in clonal rat anterior pituitary cells (GH3/B6). Pflügers Arch - Eur J Physiol 442, 577–587 (2001). https://doi.org/10.1007/s004240100567
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DOI: https://doi.org/10.1007/s004240100567