Korean J Nephrol.
2007 Jul;26(4):398-403.
Role of KCa Channels in SNAP-Induced Relaxation of Aorta from Renal Hypertensive Rats
- Affiliations
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- 1Department of Physiology, College of Medicine, Chosun University, Gwangju, Korea. chyum@chosun.ac.kr
- 2Department of Internal Medicine, College of Medicine, Chosun University, Gwangju, Korea.
Abstract
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PURPOSE: S-nitroso-N-acetylpenicillamine (SNAP), a nitric oxide (NO) donor, is thought to relax vascular smooth muscle by stimulation of soluble guanylate cyclase, accumulation of its product cyclic GMP (cGMP) level. Evidence has emerged that NO-induced vasodilatation is also mediated by stimulating Ca2+-activated K+ (KCa) channels directly or indirectly through cGMP. The aim of the present study was to investigate possible involvement or alteration of KCa channels in the mechanism of vasodilation induced by SNAP in two-kidney, one-clip (2K1C) hypertensive rats.
METHODS
2K1C hypertension was made by clipping the left renal artery and age-matched control rats received a sham treatment. Using rings prepared from thoracic aortae, we studied changes in isometric tension of the rings in response to SNAP to evaluate effects of a soluble guanylate cyclase inhibitor methylene blue (MB), and a specific blocker of KCa channel iberiotoxin (ITX).
RESULTS
Aortic rings from 2K1C hypertensive and sham-clipped control rats precontracted with phenylephrine showed similar relaxation to SNAP. MB markedly suppressed the SNAP-induced relaxation in both groups, leaving about 30% of MB-resistant relaxation. ITX nearly completely eliminated the MB-resistant relaxation in control rats, but it did not affect 2K1C rats.
CONCLUSION
These results suggest that SNAP-induced vasorelaxation is mediated through cGMP- dependent and cGMP-independent KCa channel involving mechanisms, the latter may be altered in 2K1C renal hypertension.
MeSH Terms
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Animals
Aorta*
Aorta, Thoracic
Cyclic GMP
Guanylate Cyclase
Humans
Hypertension
Hypertension, Renal
Methylene Blue
Muscle, Smooth, Vascular
Nitric Oxide
Phenylephrine
Placebos
Potassium Channels, Calcium-Activated
Rats*
Relaxation*
Renal Artery
S-Nitroso-N-Acetylpenicillamine
Tissue Donors
Vasodilation
Cyclic GMP
Guanylate Cyclase
Methylene Blue
Nitric Oxide
Phenylephrine
Placebos
Potassium Channels, Calcium-Activated
S-Nitroso-N-Acetylpenicillamine
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