Molecular analysis of ATP-sensitive K+ channel subunits expressed in mouse portal vein

• Published in: Vascular pharmacology 2015-12, Vol.75, p.29-39
• Main Authors: Yamamoto, Tadashi, Takahara, Kohei, Inai, Tetsuichiro, Node, Koichi, Teramoto, Noriyoshi
• Format: Article
• Language: English
• Subjects: Adamantane - analogs & derivatives; Adamantane - pharmacology; Animals; ATP-sensitive K+ channels; Cardiovascular; Glyburide - pharmacology; Imidazoles - pharmacology; KATP Channels - physiology; KIR6.1; Male; Mice; Mice, Inbred BALB C; Morpholines - pharmacology; Muscle, Smooth, Vascular - metabolism; Myocytes, Smooth Muscle - drug effects; Myocytes, Smooth Muscle - metabolism; Patch-Clamp Techniques; Pinacidil - pharmacology; Portal Vein - metabolism; Real-Time Polymerase Chain Reaction; Sulfonylurea Receptors - metabolism; SUR2B; Thioamides - pharmacology; Vascular smooth muscle cells
• ISSN: 1537-1891; 1879-3649
• DOI: 10.1016/j.vph.2015.06.018

Abstract Background Several combinations of inwardly rectifying K+ channel 6.x family pore-forming (KIR 6.x) subunits associated with sulphonylurea receptor (SUR.x) subunits have been detected among ATP-sensitive K+ (KATP ) channels. It remains to be established which of these is expressed in native vascular smooth muscle. Methods Pharmacological and electrophysiological properties of KATP channels in mouse portal vein were investigated using tension measurements and patch-clamp techniques. Molecular biological analyses were also performed to investigate the structural properties of these channels. Results Spontaneous contractions in mouse portal vein were reversibly reduced by pinacidil and MCC-134, and the pinacidil-induced relaxation was antagonized by glibenclamide and U-37883A. In cell-attached mode, pinacidil activated glibenclamide-sensitive K+ channels with a conductance (35 pS) similar to that of KIR 6.1. RT-PCR analysis revealed the expression of KIR 6.1, KIR 6.2 and SUR2B transcripts. Using real-time PCR methods, the quantitative expression of KIR 6.1 was much greater than that of KIR 6.2. Immunohistochemical studies indicated the presence of KIR 6.1 and SUR2B proteins in the smooth muscle layers of mouse portal vein and in single smooth muscle cells dispersed from mouse portal vein. Conclusions The results indicate that native KATP channels in mouse portal vein are likely to be composed of a heterocomplex of KIR 6.1 and SUR2B subunits.