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Basolateral ion transport mechanisms during fluid secretion by Drosophila Malpighian tubules: Na+ recycling, Na+:K+:2Cl- cotransport and Cl- conductance.
J Exp Biol. 2004 Jul; 207(Pt 15):2599-609.JE

Abstract

Mechanisms of ion transport during primary urine formation by the Malpighian tubule of Drosophila melanogaster were analyzed through measurements of fluid secretion rate, transepithelial ion flux, basolateral membrane potential (V(bl)) and intracellular activities of K(+) (a(K)(i)) and Cl(-) (a(Cl)(i)). Calculation of the electrochemical potentials for both ions permitted assessment of the possible contributions of K(+) channels, Na(+):K(+):2Cl(-) cotransport, and K(+):Cl(-) cotransport, to net transepithelial ion secretion across the basolateral membrane. The data show that passive movement of both K(+) and Cl(-) from cell to bath is favoured across the basolateral membrane, indicating that both ions are actively transported into the cell. Contributions of basolateral K(+) channels or K(+):Cl(-) cotransporters to net transepithelial ion secretion can be ruled out. After prior exposure of tubules to ouabain, subsequent addition of bumetanide reduced fluid secretion rate, K(+) flux and Na(+) flux, indicating a role for a Na(+):K(+):2Cl(-) cotransporter in fluid secretion. Addition of the K(+) channel blocker Ba(2+) had no effect on a(K)(i) or a(Cl)(i). Addition of Ba(2+) unmasked a basolateral Cl(-) conductance and the hyperpolarization of V(bl) in response to Ba(2+) was Cl(-)-dependent. A new model for fluid secretion proposes that K(+) and Cl(-) cross the basolateral membrane through a Na(+)-driven Na(+):K(+):2Cl(-) cotransporter and that most of the Na(+) that enters the cells is returned to the bath through the Na(+)/K(+)-ATPase.

Authors+Show Affiliations

Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada, L8S 4K1.No affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

15201292

Citation

Ianowski, Juan P., and Michael J. O'Donnell. "Basolateral Ion Transport Mechanisms During Fluid Secretion By Drosophila Malpighian Tubules: Na+ Recycling, Na+:K+:2Cl- Cotransport and Cl- Conductance." The Journal of Experimental Biology, vol. 207, no. Pt 15, 2004, pp. 2599-609.
Ianowski JP, O'Donnell MJ. Basolateral ion transport mechanisms during fluid secretion by Drosophila Malpighian tubules: Na+ recycling, Na+:K+:2Cl- cotransport and Cl- conductance. J Exp Biol. 2004;207(Pt 15):2599-609.
Ianowski, J. P., & O'Donnell, M. J. (2004). Basolateral ion transport mechanisms during fluid secretion by Drosophila Malpighian tubules: Na+ recycling, Na+:K+:2Cl- cotransport and Cl- conductance. The Journal of Experimental Biology, 207(Pt 15), 2599-609.
Ianowski JP, O'Donnell MJ. Basolateral Ion Transport Mechanisms During Fluid Secretion By Drosophila Malpighian Tubules: Na+ Recycling, Na+:K+:2Cl- Cotransport and Cl- Conductance. J Exp Biol. 2004;207(Pt 15):2599-609. PubMed PMID: 15201292.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Basolateral ion transport mechanisms during fluid secretion by Drosophila Malpighian tubules: Na+ recycling, Na+:K+:2Cl- cotransport and Cl- conductance. AU - Ianowski,Juan P, AU - O'Donnell,Michael J, PY - 2004/6/18/pubmed PY - 2005/2/25/medline PY - 2004/6/18/entrez SP - 2599 EP - 609 JF - The Journal of experimental biology JO - J Exp Biol VL - 207 IS - Pt 15 N2 - Mechanisms of ion transport during primary urine formation by the Malpighian tubule of Drosophila melanogaster were analyzed through measurements of fluid secretion rate, transepithelial ion flux, basolateral membrane potential (V(bl)) and intracellular activities of K(+) (a(K)(i)) and Cl(-) (a(Cl)(i)). Calculation of the electrochemical potentials for both ions permitted assessment of the possible contributions of K(+) channels, Na(+):K(+):2Cl(-) cotransport, and K(+):Cl(-) cotransport, to net transepithelial ion secretion across the basolateral membrane. The data show that passive movement of both K(+) and Cl(-) from cell to bath is favoured across the basolateral membrane, indicating that both ions are actively transported into the cell. Contributions of basolateral K(+) channels or K(+):Cl(-) cotransporters to net transepithelial ion secretion can be ruled out. After prior exposure of tubules to ouabain, subsequent addition of bumetanide reduced fluid secretion rate, K(+) flux and Na(+) flux, indicating a role for a Na(+):K(+):2Cl(-) cotransporter in fluid secretion. Addition of the K(+) channel blocker Ba(2+) had no effect on a(K)(i) or a(Cl)(i). Addition of Ba(2+) unmasked a basolateral Cl(-) conductance and the hyperpolarization of V(bl) in response to Ba(2+) was Cl(-)-dependent. A new model for fluid secretion proposes that K(+) and Cl(-) cross the basolateral membrane through a Na(+)-driven Na(+):K(+):2Cl(-) cotransporter and that most of the Na(+) that enters the cells is returned to the bath through the Na(+)/K(+)-ATPase. SN - 0022-0949 UR - https://www.unboundmedicine.com/medline/citation/15201292/Basolateral_ion_transport_mechanisms_during_fluid_secretion_by_Drosophila_Malpighian_tubules:_Na+_recycling_Na+:K+:2Cl__cotransport_and_Cl__conductance_ L2 - http://jeb.biologists.org/cgi/pmidlookup?view=long&pmid=15201292 DB - PRIME DP - Unbound Medicine ER -