| Abstrakt: |
The membrane potential V the cytosolic pH (pH), the transference numbers ( t) for K, Cl and Na/ non-selective cation (NSC) and the pH-sensitivity of V were investigated in transitional cells from the vestibular labyrinth of the gerbil. V, pH, $$t_{K^ + } , t_{Cl^ - } , t_{Na^ + /NSC} $$ , and the pH sensitivity of V were under control conditions were −92±1 mV ( n=89 cells), pH 7.13±0.07 ( n=11 epithelia), 0.87±0.02 ( n=22), 0.02±0.01 ( n=19), 0.01±0.01 ( n=24) and −5 mV/pH unit ( n=13 cells/ n=11 epithelia), respectively. In the presence of 100 μmol/l Ba the corresponding values were: −70±1 mV ( n=32), pH 7.16±0.08 ( n=6), 0.31±0.05 ( n=4), 0.06±0.01 ( n=6), 0.20±0.03 ( n=10) and -16 mV/pH-unit ( n=15/ n=6). In the presence of 500 μmol/l amiloride the corresponding values were: −72±2mV ( n=34), pH 7.00±0.07 ( n=5), 0.50±0.04 ( n=6), 0.04±0.01 ( n=11), 0.28±0.04 ( n=9) and −26 mV/pH-unit ( n=20/ n=5). In the presence of 20 mmol/l propionate plus amiloride the corresponding values were: −61±2 mV ( n=27), pH 6.72±0.06 ( n=5), 0.30±0.02 ( n=6), 0.06±0.01 ( n=5) and 0.40±0.02 ( n=8), respectively. V was depolarized and $$t_{K^ + } $$ and pH decreased due to (a) addition of 1 mmol/l amiloride in 150 mmol/l Na by 38±1 mV ( n=8), from 0.82±0.02 to 0.17±0.02 ( n=8) and by 0.13±0.01 pH unit ( n=6), respectively; (b) reduction of [Na] from 150 to 1.5 mmol/l by 3.3±0.5 mV ( n=30), from 0.83±0.02 to 0.75±0.04 ( n=9) and by 0.33±0.07 pH unit ( n=4), respectively and (c) addition of 1 mmol/l amiloride in 1.5 mmol/l Na by 20±1 mV ( n=11) and from 0.83±0.03 to 0.53±0.02 ( n=5), respectively. These data suggest that the K conductance is directly inhibited by amiloride and Ba and that Ba and amiloride uncover or induce a pH-sensitive and a Na/NSC conductance which may or may not be the same entity. [ABSTRACT FROM AUTHOR] |
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