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Secretion by the Malpighian tubules of Rhodnius prolixus stal: electrical events.
J Exp Biol. 1984 May; 110:275-90.JE

Abstract

Transepithelial and intracellular potentials have been simultaneously recorded from Rhodnius upper Malpighian tubules before and after stimulation of fluid secretion. The transepithelial electrical response to the diuretic hormone mimic 5-hydroxytryptamine (5-HT) was triphasic; recordings of intracellular potential changes indicated that the three phases represented successive events at the apical membrane. Depolarizations produced by increasing the bathing medium potassium concentration indicated that the basal membrane was much more permeable to potassium than to sodium. Electrical responses to chloride-free saline were inconsistent with a significant basal membrane chloride permeability. Chloride movements across the basal membrane were opposed by an electrical gradient of about 65 mV. The results of experiments in which tubules were exposed to chloride-free saline or sodium-free saline suggested that chloride entry into the cells was linked to the entry of Na+ and K+. The effects of furosemide and bumetanide upon secretion and potential changes suggested that chloride crossed the basal membrane through co-transport with Na+ and K+. Chloride probably crosses the apical membrane into the lumen passively in response to a favourable electrical gradient of about 35 mV. Cations must be actively pumped into the lumen against an electrical gradient of 35 mV. Our results support previous evidence for an apical cation pump which actively transports Na and K into the lumen. A tentative model of ionic movements during fluid secretion is presented. It is suggested that the apical cation pump maintains sodium at low intracellular concentrations, thereby maintaining a favourable gradient for entry of Na+ through the proposed basal co-transport step. The suggested stoichiometry is Na+:K+:2 Cl-.

Authors

No affiliation info availableNo affiliation info available

Pub Type(s)

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

Language

eng

PubMed ID

6379094

Citation

O'Donnell, M J., and S H. Maddrell. "Secretion By the Malpighian Tubules of Rhodnius Prolixus Stal: Electrical Events." The Journal of Experimental Biology, vol. 110, 1984, pp. 275-90.
O'Donnell MJ, Maddrell SH. Secretion by the Malpighian tubules of Rhodnius prolixus stal: electrical events. J Exp Biol. 1984;110:275-90.
O'Donnell, M. J., & Maddrell, S. H. (1984). Secretion by the Malpighian tubules of Rhodnius prolixus stal: electrical events. The Journal of Experimental Biology, 110, 275-90.
O'Donnell MJ, Maddrell SH. Secretion By the Malpighian Tubules of Rhodnius Prolixus Stal: Electrical Events. J Exp Biol. 1984;110:275-90. PubMed PMID: 6379094.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Secretion by the Malpighian tubules of Rhodnius prolixus stal: electrical events. AU - O'Donnell,M J, AU - Maddrell,S H, PY - 1984/5/1/pubmed PY - 1984/5/1/medline PY - 1984/5/1/entrez SP - 275 EP - 90 JF - The Journal of experimental biology JO - J Exp Biol VL - 110 N2 - Transepithelial and intracellular potentials have been simultaneously recorded from Rhodnius upper Malpighian tubules before and after stimulation of fluid secretion. The transepithelial electrical response to the diuretic hormone mimic 5-hydroxytryptamine (5-HT) was triphasic; recordings of intracellular potential changes indicated that the three phases represented successive events at the apical membrane. Depolarizations produced by increasing the bathing medium potassium concentration indicated that the basal membrane was much more permeable to potassium than to sodium. Electrical responses to chloride-free saline were inconsistent with a significant basal membrane chloride permeability. Chloride movements across the basal membrane were opposed by an electrical gradient of about 65 mV. The results of experiments in which tubules were exposed to chloride-free saline or sodium-free saline suggested that chloride entry into the cells was linked to the entry of Na+ and K+. The effects of furosemide and bumetanide upon secretion and potential changes suggested that chloride crossed the basal membrane through co-transport with Na+ and K+. Chloride probably crosses the apical membrane into the lumen passively in response to a favourable electrical gradient of about 35 mV. Cations must be actively pumped into the lumen against an electrical gradient of 35 mV. Our results support previous evidence for an apical cation pump which actively transports Na and K into the lumen. A tentative model of ionic movements during fluid secretion is presented. It is suggested that the apical cation pump maintains sodium at low intracellular concentrations, thereby maintaining a favourable gradient for entry of Na+ through the proposed basal co-transport step. The suggested stoichiometry is Na+:K+:2 Cl-. SN - 0022-0949 UR - https://www.unboundmedicine.com/medline/citation/6379094/Secretion_by_the_Malpighian_tubules_of_Rhodnius_prolixus_stal:_electrical_events_ L2 - http://jeb.biologists.org/cgi/pmidlookup?view=long&pmid=6379094 DB - PRIME DP - Unbound Medicine ER -