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Nitric oxide relaxes circular smooth muscle of rat distal colon through RhoA/Rho-kinase independent Ca2+ desensitisation.
- Source :
-
British journal of pharmacology [Br J Pharmacol] 2005 Feb; Vol. 144 (4), pp. 588-94. - Publication Year :
- 2005
-
Abstract
- 1. The aim of this study in circular smooth muscle of rat distal colon was to determine whether Ca(2+) desensitisation, in addition to mechanisms lowering cytosolic free Ca(2+) concentration ([Ca(2+)](cyt)), was involved in the relaxation elicited by nitric oxide (NO). Changes in isometric tension and [Ca(2+)](cyt) were recorded simultaneously in fura-2-loaded strips. 2. In methacholine (10(-5) M)-precontracted preparations, exogenous NO (10(-4) M), adenosine 5'-triphosphate (ATP; 10(-3) M) and electrical field stimulation (EFS; 1 ms, 40 V, 4 Hz, 1 min) induced a decrease in smooth muscle tension, which was accompanied by a fall in [Ca(2+)](cyt). 3. The sarcoplasmic/endoplasmic reticulum Ca(2+) ATP-ase (SERCA) inhibitor thapsigargin (10(-6) M) did not exert an influence on the decrease in tension produced by exogenous NO, but significantly attenuated the fall in [Ca(2+)](cyt). Both the relaxation and the fall in [Ca(2+)](cyt) to ATP and EFS were unaffected by thapsigargin. 4. Calyculin-A (10(-6) M), a myosin light chain phosphatase (MLCP) inhibitor, significantly reduced the decrease in tension elicited by exogenous NO, but did not alter the fall in [Ca(2+)](cyt) to exogenous NO. Inactivating RhoA by exoenzyme C3 (2 mug ml(-1)) or inhibiting Rho-kinase with (+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl) cyclohexanecarboxamide dihydrochloride monohydrate (Y-27632; 10(-5) M) had no effect on the decrease of both tension and [Ca(2+)](cyt) generated by exogenous NO. 5. This paper demonstrates that a RhoA/Rho-kinase independent Ca(2+) desensitisation pathway contributes to the relaxation by NO in circular smooth muscle strips of rat distal colon.
- Subjects :
- Adenosine Triphosphate metabolism
Animals
Electric Stimulation
Enzyme Inhibitors pharmacology
In Vitro Techniques
Intracellular Signaling Peptides and Proteins
Male
Muscle Relaxation drug effects
Nitric Oxide pharmacology
Protein Serine-Threonine Kinases antagonists & inhibitors
Rats
Rats, Inbred Strains
rho-Associated Kinases
Calcium metabolism
Colon enzymology
Colon metabolism
Colon physiology
Muscle Relaxation physiology
Muscle, Smooth enzymology
Muscle, Smooth metabolism
Muscle, Smooth physiology
Nitric Oxide physiology
Protein Serine-Threonine Kinases metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0007-1188
- Volume :
- 144
- Issue :
- 4
- Database :
- MEDLINE
- Journal :
- British journal of pharmacology
- Publication Type :
- Academic Journal
- Accession number :
- 15655498
- Full Text :
- https://doi.org/10.1038/sj.bjp.0706111