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Intracellular ion activities in Malpighian tubule cells of Rhodnius prolixus: evaluation of Na+-K+-2Cl- cotransport across the basolateral membrane.
J Exp Biol. 2002 Jun; 205(Pt 11):1645-55.JE

Abstract

Intracellular ion activities (a(ion)) and basolateral membrane potential (Vbl) were measured in Malpighian tubule cells of Rhodnius prolixus using double-barrelled ion-selective microelectrodes. In saline containing 103 mmol l(-1) Na+, 6 mmol l(-1) K+ and 93 mmol l(-1) Cl-, intracellular ion activities in unstimulated upper Malpighian tubules were 21, 86 and 32 mmol l(-1), respectively. In serotonin-stimulated tubules, aCl was unchanged, whereas aNa increased to 33 mmol l(-1) and aK declined to 71 mmol l(-1). Vbl was -59 mV and -63 mV for unstimulated and stimulated tubules, respectively. Calculated electrochemical potentials (deltamuF) favour passive movement of Na+ into the cell and passive movement of Cl- out of the cell in both unstimulated and serotonin-stimulated tubules. Passive movement of K+ out of the cell is favoured in unstimulated tubules. In stimulated tubules, deltamuF for K+ is close to 0 mV. The thermodynamic feasibilities of Na+-K+-2Cl-, Na+-Cl- and K+-Cl- cotransporters were evaluated by calculating the net electrochemical potential (deltamu(net)/F) for each transporter. Our results show that a Na+-K+-2Cl- or a Na+-Cl- cotransporter but not a K+-Cl- cotransporter would permit the movement of ions into the cell in stimulated tubules. The effects of Ba2+ and ouabain on Vbl and rates of fluid and ion secretion show that net entry of K+ through ion channels or the Na+/K+-ATPase can be ruled out in stimulated tubules. Maintenance of intracellular Cl- activity was dependent upon the presence of both Na+ and K+ in the bathing saline. Bumetanide reduced the fluxes of both Na+ and K+. Taken together, the results support the involvement of a basolateral Na+-K+-2Cl- cotransporter in serotonin-stimulated fluid secretion by Rhodnius prolixus Malpighian tubules.

Authors+Show Affiliations

Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4K1. ianowsjp@mcmaster.caNo affiliation info availableNo affiliation info available

Pub Type(s)

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

Language

eng

PubMed ID

12000809

Citation

Ianowski, Juan P., et al. "Intracellular Ion Activities in Malpighian Tubule Cells of Rhodnius Prolixus: Evaluation of Na+-K+-2Cl- Cotransport Across the Basolateral Membrane." The Journal of Experimental Biology, vol. 205, no. Pt 11, 2002, pp. 1645-55.
Ianowski JP, Christensen RJ, O'Donnell MJ. Intracellular ion activities in Malpighian tubule cells of Rhodnius prolixus: evaluation of Na+-K+-2Cl- cotransport across the basolateral membrane. J Exp Biol. 2002;205(Pt 11):1645-55.
Ianowski, J. P., Christensen, R. J., & O'Donnell, M. J. (2002). Intracellular ion activities in Malpighian tubule cells of Rhodnius prolixus: evaluation of Na+-K+-2Cl- cotransport across the basolateral membrane. The Journal of Experimental Biology, 205(Pt 11), 1645-55.
Ianowski JP, Christensen RJ, O'Donnell MJ. Intracellular Ion Activities in Malpighian Tubule Cells of Rhodnius Prolixus: Evaluation of Na+-K+-2Cl- Cotransport Across the Basolateral Membrane. J Exp Biol. 2002;205(Pt 11):1645-55. PubMed PMID: 12000809.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Intracellular ion activities in Malpighian tubule cells of Rhodnius prolixus: evaluation of Na+-K+-2Cl- cotransport across the basolateral membrane. AU - Ianowski,Juan P, AU - Christensen,Robert J, AU - O'Donnell,Michael J, PY - 2002/5/10/pubmed PY - 2002/12/11/medline PY - 2002/5/10/entrez SP - 1645 EP - 55 JF - The Journal of experimental biology JO - J Exp Biol VL - 205 IS - Pt 11 N2 - Intracellular ion activities (a(ion)) and basolateral membrane potential (Vbl) were measured in Malpighian tubule cells of Rhodnius prolixus using double-barrelled ion-selective microelectrodes. In saline containing 103 mmol l(-1) Na+, 6 mmol l(-1) K+ and 93 mmol l(-1) Cl-, intracellular ion activities in unstimulated upper Malpighian tubules were 21, 86 and 32 mmol l(-1), respectively. In serotonin-stimulated tubules, aCl was unchanged, whereas aNa increased to 33 mmol l(-1) and aK declined to 71 mmol l(-1). Vbl was -59 mV and -63 mV for unstimulated and stimulated tubules, respectively. Calculated electrochemical potentials (deltamuF) favour passive movement of Na+ into the cell and passive movement of Cl- out of the cell in both unstimulated and serotonin-stimulated tubules. Passive movement of K+ out of the cell is favoured in unstimulated tubules. In stimulated tubules, deltamuF for K+ is close to 0 mV. The thermodynamic feasibilities of Na+-K+-2Cl-, Na+-Cl- and K+-Cl- cotransporters were evaluated by calculating the net electrochemical potential (deltamu(net)/F) for each transporter. Our results show that a Na+-K+-2Cl- or a Na+-Cl- cotransporter but not a K+-Cl- cotransporter would permit the movement of ions into the cell in stimulated tubules. The effects of Ba2+ and ouabain on Vbl and rates of fluid and ion secretion show that net entry of K+ through ion channels or the Na+/K+-ATPase can be ruled out in stimulated tubules. Maintenance of intracellular Cl- activity was dependent upon the presence of both Na+ and K+ in the bathing saline. Bumetanide reduced the fluxes of both Na+ and K+. Taken together, the results support the involvement of a basolateral Na+-K+-2Cl- cotransporter in serotonin-stimulated fluid secretion by Rhodnius prolixus Malpighian tubules. SN - 0022-0949 UR - https://www.unboundmedicine.com/medline/citation/12000809/Intracellular_ion_activities_in_Malpighian_tubule_cells_of_Rhodnius_prolixus:_evaluation_of_Na+_K+_2Cl__cotransport_across_the_basolateral_membrane_ L2 - http://jeb.biologists.org/cgi/pmidlookup?view=long&pmid=12000809 DB - PRIME DP - Unbound Medicine ER -