108-pS channel in brown fat mitochondria might Be identical to the inner membrane anion channel.
Single-channel and whole-mitoplast patch-clamp recordings were employed to characterize the 108-pS (Cl-) channel in brown fat mitochondrial mitoplasts. We demonstrated the ability of this channel to conduct di- and trivalent anions, such as sulfate, phosphate, and benzenetricarboxylates, and its blockage by propranolol, 1,4-dihydropyridine-type Ca2+ antagonists, and Cibacron blue. Moreover, we have revealed its pH dependence for the first time. As a basis for the characteristic potential dependence of the whole-mitoplast current, we identified an open probability, increasing with depolarizing (positive) potentials, Eh, and being almost zero in the hyperpolarizing range. Events at negative Eh exhibit a short flickering behavior, whereas at positive Eh, they become much longer. This voltage dependence is influenced by pH in such a way that, at acidic pH, the 108-pS channel possesses a low open probability throughout the observed potential range, whereas at alkaline pH, the channel switches to long openings, even at a negative potential. All these properties lead us to conclude that the inner membrane anion channel, which has been characterized only by light scattering studies, and the 108-pS inner membrane channel, which has been characterized electrophysiologically, are one and the same process.
Borecký
J
J
Department of Membrane Transport Biophysics, Institute of Physiology, Academy of Sciences of Czech Republic, CZ-14220 Prague 4, Czech Republic.
Jezek
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Siemen
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D002001:Adipose Tissue, Brown / Q000378:metabolism*; D000818:Animals; D006224:Cricetinae; D006863:Hydrogen-Ion Concentration; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008647:Mesocricetus; D008928:Mitochondria / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D014227:Triazines / Q000494:pharmacology
D007473:Ion Channels; D014227:Triazines; C012842:Cibacron Blue F 3GA; D011433:Propranolol; D009543:Nifedipine