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Nitric Oxide Links the Apical Na+ Transport to the Basolateral K+ Conductance in the Rat Cortical Collecting Duct
- Source :
- The Journal of General Physiology
- Publication Year :
- 1997
- Publisher :
- Rockefeller University Press, 1997.
-
Abstract
- We have used the patch clamp technique to study the effects of inhibiting the apical Na+ transport on the basolateral small-conductance K+ channel (SK) in cell-attached patches in cortical collecting duct (CCD) of the rat kidney. Application of 50 microM amiloride decreased the activity of SK, defined as nPo (a product of channel open probability and channel number), to 61% of the control value. Application of 1 microM benzamil, a specific Na+ channel blocker, mimicked the effects of amiloride and decreased the activity of the SK to 62% of the control value. In addition, benzamil reduced intracellular Na+ concentration from 15 to 11 mM. The effect of amiloride was not the result of a decrease in intracellular pH, since addition 50 microM 5-(n-ethyl-n-isopropyl) amiloride (EIPA), an agent that specifically blocks the Na/H exchanger, did not alter the channel activity. The inhibitory effect of amiloride depends on extracellular Ca2+ because removal of Ca2+ from the bath abolished the effect. Using Fura-2 AM to measure the intracellular Ca2+, we observed that amiloride and benzamil significantly decreased intracellular Ca2+ in the Ca2+-containing solution but had no effect in a Ca2+-free bath. Furthermore, raising intracellular Ca2+ from 10 to 50 and 100 nM with ionomycin increased the activity of the SK in cell-attached patches but not in excised patches, suggesting that changes in intracellular Ca2+ are responsible for the effects on SK activity of inhibition of the Na+ transport. Since the neuronal form of nitric oxide synthase (nNOS) is expressed in the CCD and the function of the nNOS is Ca2+ dependent, we examined whether the effects of amiloride or benzamil were mediated by the NO-cGMP-dependent pathways. Addition of 10 microM S-nitroso-n-acetyl-penicillamine (SNAP) or 100 microM 8-bromoguanosine 3':5'-cyclic monophosphate (8Br-cGMP) completely restored channel activity when it had been decreased by either amiloride or benzamil. Finally, addition of SNAP caused a significant increase in channel activity in the Ca2+-free bath solution. We conclude that Ca2+-dependent NO generation mediates the effect of inhibiting the apical Na+ transport on the basolateral SK in the rat CCD.
- Subjects :
- Epithelial sodium channel
medicine.medical_specialty
Patch-Clamp Techniques
Potassium Channels
K+ channel
Physiology
Intracellular pH
S-Nitroso-N-Acetylpenicillamine
030204 cardiovascular system & hematology
Nitric Oxide
patch clamp
Sodium Channels
Article
collecting duct
Amiloride
Rats, Sprague-Dawley
03 medical and health sciences
chemistry.chemical_compound
0302 clinical medicine
Internal medicine
Benzamil
medicine
Animals
Channel blocker
Na+ channel
Enzyme Inhibitors
Kidney Tubules, Collecting
Diuretics
Cyclic GMP
030304 developmental biology
0303 health sciences
nitric oxide synthase
Penicillamine
Sodium
Biological Transport
Potassium channel
Rats
Specific Pathogen-Free Organisms
Sodium–hydrogen antiporter
NG-Nitroarginine Methyl Ester
Endocrinology
chemistry
Ionomycin
Potassium
Biophysics
Calcium
Anti-Arrhythmia Agents
medicine.drug
Subjects
Details
- ISSN :
- 15407748 and 00221295
- Volume :
- 110
- Database :
- OpenAIRE
- Journal :
- Journal of General Physiology
- Accession number :
- edsair.doi.dedup.....4b1c0b4b31026775f5fc6dafbdf7c779
- Full Text :
- https://doi.org/10.1085/jgp.110.6.717