Abstract
Extracellular ATP in the cortical collecting duct can inhibit epithelial sodium channels (ENaC) but also stimulate calcium-activated chloride channels (CACC). The relationship between ATP-mediated regulation of ENaC and CACC activity in cortical collecting duct cells has not been clearly defined. We used the mpkCCD c14 cortical collecting duct cell line to determine effects of ATP on sodium (Na +) and chloride (Cl -) transport with an Ussing chamber system. ATP, at a concentration of 10 -6 M or less, did not inhibit ENaC-mediated short-circuit current (I sc) but instead stimulated a transient increase in I sc. The macroscopic current-voltage relationship for ATP-inducible current demonstrated that the direction of this ATP response changes from positive to negative when transepithelial voltage (V te) is clamped to less than -10 mV. We hypothesized that this negative V te might be found under conditions of aldosterone stimulation. We next stimulated mpkCCD c14 cells with aldosterone (10 -6 M) and then clamped the V te to -50 mV, the Vte of aldosterone-stimulated cells under open-circuit conditions. ATP (10 -6 M) induced a transient increase in negative clamp current, which could be inhibited by flufenamic acid (CACC inhibitor) and BAPTA-AM (calcium chelator), suggesting that ATP stimulates Cl - absorption through CACC. Together, our findings suggest that the status of ENaC activity, by controlling V te, may dictate the direction of ATP-stimulated Cl - transport. This interplay between aldosterone and purinergic signaling pathways may be relevant for regulating NaCl transport in cortical collecting duct cells under different states of extracellular fluid volume.
| Original language | English (US) |
|---|---|
| Journal | American Journal of Physiology - Renal Physiology |
| Volume | 303 |
| Issue number | 4 |
| DOIs | |
| State | Published - Aug 15 2012 |
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Keywords
- CACC
- ENaC
- P2Y receptor
ASJC Scopus subject areas
- Physiology
- Urology
Cite this
Differential effects of extracellular ATP on chloride transport in cortical collecting duct cells. / Rajagopal, Madhumitha; Kathpalia, Paru P.; Widdicombe, Jonathan; Pao, Alan C.
In: American Journal of Physiology - Renal Physiology, Vol. 303, No. 4, 15.08.2012.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Differential effects of extracellular ATP on chloride transport in cortical collecting duct cells
AU - Rajagopal, Madhumitha
AU - Kathpalia, Paru P.
AU - Widdicombe, Jonathan
AU - Pao, Alan C.
PY - 2012/8/15
Y1 - 2012/8/15
N2 - Extracellular ATP in the cortical collecting duct can inhibit epithelial sodium channels (ENaC) but also stimulate calcium-activated chloride channels (CACC). The relationship between ATP-mediated regulation of ENaC and CACC activity in cortical collecting duct cells has not been clearly defined. We used the mpkCCD c14 cortical collecting duct cell line to determine effects of ATP on sodium (Na +) and chloride (Cl -) transport with an Ussing chamber system. ATP, at a concentration of 10 -6 M or less, did not inhibit ENaC-mediated short-circuit current (I sc) but instead stimulated a transient increase in I sc. The macroscopic current-voltage relationship for ATP-inducible current demonstrated that the direction of this ATP response changes from positive to negative when transepithelial voltage (V te) is clamped to less than -10 mV. We hypothesized that this negative V te might be found under conditions of aldosterone stimulation. We next stimulated mpkCCD c14 cells with aldosterone (10 -6 M) and then clamped the V te to -50 mV, the Vte of aldosterone-stimulated cells under open-circuit conditions. ATP (10 -6 M) induced a transient increase in negative clamp current, which could be inhibited by flufenamic acid (CACC inhibitor) and BAPTA-AM (calcium chelator), suggesting that ATP stimulates Cl - absorption through CACC. Together, our findings suggest that the status of ENaC activity, by controlling V te, may dictate the direction of ATP-stimulated Cl - transport. This interplay between aldosterone and purinergic signaling pathways may be relevant for regulating NaCl transport in cortical collecting duct cells under different states of extracellular fluid volume.
AB - Extracellular ATP in the cortical collecting duct can inhibit epithelial sodium channels (ENaC) but also stimulate calcium-activated chloride channels (CACC). The relationship between ATP-mediated regulation of ENaC and CACC activity in cortical collecting duct cells has not been clearly defined. We used the mpkCCD c14 cortical collecting duct cell line to determine effects of ATP on sodium (Na +) and chloride (Cl -) transport with an Ussing chamber system. ATP, at a concentration of 10 -6 M or less, did not inhibit ENaC-mediated short-circuit current (I sc) but instead stimulated a transient increase in I sc. The macroscopic current-voltage relationship for ATP-inducible current demonstrated that the direction of this ATP response changes from positive to negative when transepithelial voltage (V te) is clamped to less than -10 mV. We hypothesized that this negative V te might be found under conditions of aldosterone stimulation. We next stimulated mpkCCD c14 cells with aldosterone (10 -6 M) and then clamped the V te to -50 mV, the Vte of aldosterone-stimulated cells under open-circuit conditions. ATP (10 -6 M) induced a transient increase in negative clamp current, which could be inhibited by flufenamic acid (CACC inhibitor) and BAPTA-AM (calcium chelator), suggesting that ATP stimulates Cl - absorption through CACC. Together, our findings suggest that the status of ENaC activity, by controlling V te, may dictate the direction of ATP-stimulated Cl - transport. This interplay between aldosterone and purinergic signaling pathways may be relevant for regulating NaCl transport in cortical collecting duct cells under different states of extracellular fluid volume.
KW - CACC
KW - ENaC
KW - P2Y receptor
UR - http://www.scopus.com/inward/record.url?scp=84865119930&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84865119930&partnerID=8YFLogxK
U2 - 10.1152/ajprenal.00062.2012
DO - 10.1152/ajprenal.00062.2012
M3 - Article
C2 - 22647633
AN - SCOPUS:84865119930
VL - 303
JO - American Journal of Physiology - Renal Fluid and Electrolyte Physiology
JF - American Journal of Physiology - Renal Fluid and Electrolyte Physiology
SN - 1931-857X
IS - 4
ER -