Opening of ATP-sensitive K+ channels (KATP+) in vascular smooth muscle allows K+ efflux with subsequent hyperpolarization, closure of voltage-sensitive Ca2+ channels (VOCs), and ensuing relaxation. KATP+ have been implicated as regulators of resting vascular tone as well as metabolic sensors which mediate vascular responsiveness. The potent vasoconstrictor peptide endothelin-1 (ET-1) may also participate in regulation of vascular tone. In previous work from this laboratory ET-1 potently contracted isolated vessels, elevated input pressure in isolated perfused gills and reduced dorsal aortic pressure in conscious trout, possibly through a gill constriction. Maximally vasorelaxant doses of the KATP+ opener pinacidil (PNC), the guanylate cyclase activator sodium nitroprusside (SNP) and the VOC blacker Verapamil (VER) relaxed unstimulated efferent branchial arteries by 46, 15 and 4%, respectively. PNC, SNP or VER pretreatment resulted in significant attenuation (p≤.05), mild attenuation or paradoxical enhancement of maximal ET-1 tension, respectively. In the untreated perfused gill, PNC reduced input pressure while SNP and VER did not. Furthermore, only PNC pretreatment fully offset subsequent input pressure elevations due to ET-1 and only PNC was effective in reversing ET-1 effects. This data suggests that KATP+ are important physiological modulators of resting tone and vasoresponsiveness in gill resistance elements of the trout.
|Original language||English (US)|
|State||Published - Dec 1 1997|
ASJC Scopus subject areas
- Molecular Biology