Table of Contents
Journal of Biophysics
Volume 2013, Article ID 913792, 16 pages
http://dx.doi.org/10.1155/2013/913792
Research Article

Potassium Current Is Not Affected by Long-Term Exposure to Ghrelin or GHRP-6 in Somatotropes GC Cells

1Laboratorio de Neuroendocrinología, Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, CP 7200, PUE, Mexico
2Laboratorio de Biología Celular, Facultad de Medicina Veterinaria y Zootecnia, Universidad Veracruzana, CP 91710, VER, Mexico

Received 1 September 2012; Accepted 17 December 2012

Academic Editor: Eaton Edward Lattman

Copyright © 2013 Belisario Domínguez Mancera et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Ghrelin is a growth hormone (GH) secretagogue (GHS) and GHRP-6 is a synthetic peptide analogue; both act through the GHS receptor. GH secretion depends directly on the intracellular concentration of Ca2+; this is determined from the intracellular reserves and by the entrance of Ca2+ through the voltage-dependent calcium channels, which are activated by the membrane depolarization. Membrane potential is mainly determined by K+ channels. In the present work, we investigated the effect of ghrelin (10 nM) or GHRP-6 (100 nM) for 96 h on functional expression of voltage-dependent K+ channels in rat somatotropes: GC cell line. Physiological patch-clamp whole-cell recording was used to register the K+ currents. With Cd2+ (1 mM) and tetrodotoxin (1 μm) in the bath solution recording, three types of currents were characterized on the basis of their biophysical and pharmacological properties. GC cells showed a K+ current with a transitory component sensitive to 4-aminopyridine, which represents ~40% of the total outgoing current; a sustained component named delayed rectifier , sensitive to tetraethylammonium; and a third type of K+ current was recorded at potentials more negative than −80 mV, permitting the entrance of K+ named inward rectifier (KIR). Chronic treatment with ghrelin or GHRP-6 did not modify the functional expression of K+ channels, without significant changes ( ) in the amplitudes of the three currents observed; in addition, there were no modifications in their biophysical properties and kinetic activation or inactivation.