Ghrelin Reduces Voltage-Gated Potassium Currents In GH3 Cells Via CGMP/PKG Pathways

Ghrelin is an endogenous GH secretagogue (GHS) to release growth hormone (GH) from pituitary somatotropes through GHS receptor. Secretion of GH is linked directly to intracellular free Ca~2+ concentration, which is determined by Ca~2+ influx and release from Ca~2+ storage sites. Ca~2+ influx is via voltage-gated Ca~2+ channels, which are activated by cell depolarization. Membrane potential is mainly determined by transmembrane K~+ channels. The present study is to investigate the in vitro effect of ghrelin on membrane voltage-gated K~+ channels of GH3 rat somatotrope cell line. Nystatin-perforated whole-cell recording configuration was used to record K~+ currents under voltage-clamp condition. In the presence of Co~2+ (1μM, Ca~2+ channel blocker), tetrodotoxin (1μM, Na~+ channel blocker) in the bath solution, two types of voltage-gated K~+ currents were identified on the basis of their biophysical kinetics and...