The erg-like potassium current in rat lactotrophs

Area of Science:

• Electrophysiology
• Molecular Biology
• Endocrinology

Background:

• The ether-à-go-go-related gene (erg)-like K+ current plays a role in pituitary cell function.
• Understanding the specific properties and regulation of this current is crucial for pituitary physiology.
• Differences may exist between native lactotrophs and clonal pituitary cell lines.

Purpose of the Study:

• To characterize the erg-like K+ current in rat lactotrophs and compare it with GH3/B6 cells.
• To investigate the effect of thyrotrophin-releasing hormone on this current.
• To examine the expression of erg-like genes in both cell types.

Main Methods:

• Patch-clamp technique was used to record K+ currents in primary cultured rat lactotrophs and GH3/B6 cells.
• The specific erg-like current was isolated using the class III antiarrhythmic E-4031.
• RT-PCR was employed to analyze the mRNA expression of rat erg genes (r-erg1, r-erg2, r-erg3).

Main Results:

• Rat lactotrophs exhibited both fast and slowly deactivating erg-like K+ current components, with the slow component's contribution being voltage-dependent.
• GH3/B6 cells showed a predominant fast deactivating component, similar to the fast component in native lactotrophs.
• Thyrotrophin-releasing hormone reduced the erg-like current in native lactotrophs via a signaling pathway independent of protein kinase A and C. Different combinations of r-erg mRNA were found in lactotrophs, while GH3/B6 cells expressed only r-erg1 and r-erg2.

Conclusions:

• GH3/B6 cells partially mimic the erg-like K+ current of native lactotrophs, but with distinct properties regarding current component contribution.
• The expression profile of erg genes differs between native lactotrophs and GH3/B6 cells.
• Thyrotrophin-releasing hormone modulates the erg-like current in lactotrophs through a novel intracellular signaling pathway.