1. Electrophysiological techniques have been applied to tsetse fly Malpighian tubules for the first time. 2. In either Cl- or SO42- Ringer, both non-perfused and perfused tubules displayed transtubular potentials (Vt) at or close to 0 mV. Exposure to cyclic AMP elicited a marked secretory response and, in SO42- Ringer, a sharp (lumen-positive) increase in Vt. In Cl- Ringer, despite more than double the secretory response, there was little or no change in Vt. 3. Replacing Cl- with SO42- Ringer, in the presence of cyclic AMP, promptly increased Vt. In perfused tubules, this occurred irrespective of the Cl- or SO42- composition of the perfusate. 4. In Cl- Ringer, the transepithelial resistance (Rtrans) was less than half that previously reported in Malpighian tubules of other species. Cyclic AMP reduced Rtrans still further, whether tubules were bathed in Cl- or SO42- Ringer. 5. Currentvoltage (I/V) plots often displayed current rectification, both before and more frequently after exposure to cyclic AMP, thus permitting estimation of both the electromotive force of the Na+ transport mechanism (ENa) and of the shunt resistance (Rshunt). Both ENa and Rshunt were markedly lower in tubules bathed in Cl- than in SO42- Ringer. Cyclic AMP was without effect on ENa and Rshunt, in either Cl- or SO42- Ringer. 6. In terms of the equivalent electrical circuit, the secretory response to cyclic AMP was due solely to a fall in resistance of the active transport pathway (Rseries). The absence of an appreciable Vt, in Cl- Ringer, is consistent with an apical Cl- shunt.
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JOURNAL ARTICLE| 01 January 1994
CONCEALED TRANSEPITHELIAL POTENTIALS AND CURRENT RECTIFICATION IN TSETSE FLY MALPIGHIAN TUBULES
Online Issn: 1477-9145
Print Issn: 0022-0949
© 1994 by Company of Biologists
J Exp Biol (1994) 186 (1): 199–213.
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L. Isaacson, S. Nicolson; CONCEALED TRANSEPITHELIAL POTENTIALS AND CURRENT RECTIFICATION IN TSETSE FLY MALPIGHIAN TUBULES. J Exp Biol 1 January 1994; 186 (1): 199–213. doi: https://doi.org/10.1242/jeb.186.1.199
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