Abstract
The influence of voltage on the conductance of toad skin was studied to identify the time course of the activation/deactivation dynamics of voltage-dependent Cl- channels located in the apical membrane of mitochondrion-rich cells in this tissue. Positive apical voltage induced an important conductance inhibition which took a few seconds to fully develop and was instantaneously released by pulse inversion to negative voltage, indicating a short-duration memory of the inhibiting factors. Sinusoidal stimulation at 23.4 mM [Cl-] showed hysteresis in the current versus voltage curves, even at very low frequency, suggesting that the rate of voltage application was also relevant for the inhibition/releasing effect to develop. We conclude that the voltage modulation of apical Cl- permeability is essentially a fast process and the apparent slow components of activation/deactivation obtained in the whole skin are a consequence of a gradual voltage build-up across the apical membrane due to voltage sharing between apical and basolateral membranes.
Highlights
It is known that hyperpolarization of toad skin epithelium leads to a slow activation of a Cl- conductive pathway [1,2,3,4,5,6,7,8,9,10,11,12]
We conclude that the voltage modulation of apical Cl- permeability is essentially a fast process and the apparent slow components of activation/deactivation obtained in the whole skin are a consequence of a gradual voltage build-up across the apical membrane due to voltage sharing between apical and basolateral membranes
Experimental evidence suggests that a minimum concentration of Cl- ions in the cytoplasm and external solution is a necessary condition for the activation of apical Cl- permeability [12,18]
Summary
It is known that hyperpolarization of toad skin epithelium leads to a slow activation of a Cl- conductive pathway [1,2,3,4,5,6,7,8,9,10,11,12]. Experimental evidence suggests that a minimum concentration of Cl- ions in the cytoplasm and external solution is a necessary condition for the activation of apical Cl- permeability [12,18]. In favor of this idea is the fact that all maneuvers eliciting Cl- permeability in the skin are associated with states in which cytoplasmic [Cl-] is presumably higher than normal. The well-known Cl- permeability activation achieved by hyperpolarizing the skin in NaCl
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Schedule a callMore From: Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas
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