An attempt to determine the mechanisms of Cl−-exit across the basolateral membrane of eel intestine: Use of different cl−-transport pathway inhibitors
✍ Scribed by Trischitta, F. ;Denaro, M. G. ;Faggio, C. ;Schettino, T.
- Publisher
- John Wiley and Sons
- Year
- 1992
- Tongue
- English
- Weight
- 796 KB
- Volume
- 264
- Category
- Article
- ISSN
- 0022-104X
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
The possible mechanisms of Cl^−^‐exit across the basolateral membrane of the enterocyte in sea water (SW) and freshwater (FW) eel intestine were investigated by observing the response of the short‐circuit current, I~sc~, equivalent to net Cl^−^‐absorption, and transepithelial voltage, V~t~, to specific or relatively specific inhibitors of different Cl^−^‐transport pathways. Serosal NPPB [5‐nitro‐2(3 phenylpropylamino)‐benzoate] (10^−4^ M), the potent blocker of Cl^−^‐channels in different epithelia, produced a negligible effect on I~sc~ and V~t~ either in presence or in absence of HCO~3~^−^ in the bathing solutions. In the presence of HCO~3~^−^ serosal bumetanide, better than furosemide and torasemide, at a concentration of 10^−4^ M inhibited I~sc~ and V~t~ by ∼90% within 15–30 min without changing the transepithelial resistance, R~t~. In HCO~3~^−^‐free solutions the drug completely collapsed I~sc~ and V~t~. The results were similar in both SW and FW eels. In SW fishes serosal SITS (2.5 × 10^−4^ M) reduced I~sc~ and V~t~ by ∼50% when HCO~3~^−^ was present in the solutions. In absence of HCO~3~^−^ SITS inhibited I~sc~ and V~t~ by ∼35%, a finding consistent with the presence of a Cl^−^‐conductance in the basolateral membrane. Under these conditions SITS inhibition disappeared after bumetanide pretreatment. There is little evidence for the presence of a basolateral K^+^‐conductance since serosal Ba^2+^ (1 mM) elicited variable effects on I~sc~ and V~t~.
The results are interpreted as evidence for the presence of bumetanide‐ and SITS‐sensitive Cl^−^‐ conductance channels in the basolateral membrane of SW and FW eel intestine which would contribute at least 35% of the net Cl^−^‐absorption. An HCO~3~^−^‐dependent Cl^−^‐transport was also identified since I~sc~ and V~t~ were reduced by ∼50% when tissues were perfused with HCO~3~^−^‐free salines. © 1992 Wiley‐Liss, Inc.