Chloride transport in toad skin (Bufo viridis). The effect of salt adaptation

TY - JOUR

T1 - Chloride transport in toad skin (Bufo viridis). The effect of salt adaptation

AU - Katz, U

AU - Larsen, Erik Hviid

PY - 1984/3

Y1 - 1984/3

N2 - The steady-state Cl- current across the skin of Bufo viridis adapted to tap water was found to be rectified. In skins bathed with NaCl Ringer on both sides, a large outward current, carried by influx of Cl-, was observed at a clamping voltage (V) of less than -50 mV (outside of the skin negative). for V = -50 mV the transepithelial Cl- conductance calculated from isotope flux measurements was 2.5 +/- 0.3 mS cm-2, N = 10. When the skin was clamped at + 50 mV the net flux of Cl- was reversed, but Cl- conductance was only 0.3 +/- 0.1 mScm-2. Flux ratio analysis indicated that the potential-activated Cl- conductance carries Cl- ions by way of passive transport. With NaCl Ringer bathing the outer surface of the skin the spontaneous potential was about -30 mV. At this potential the Cl- conductance of the skin was about half of its maximum value. The time course of Cl- current activation following a fast, stepwise change of V from 50 mV to a potential below O mV showed an initial delay of a few seconds, and proceeded with a halftime (T 1/2) which varied as a bell-shaped function of V. The maximum T 1/2 was about 100 s for V = -10 mV in skins exposed to KCl Ringer on the outside. Following adaptation of the toads to a 250 mM-NaCl solution, the fully activated Cl- conductance of the skin was greatly reduced, and the conductance-voltage curve was shifted to the left along the voltage-axis. With NaCl Ringer on the outside the spontaneous potential was about -20 mV, and Cl- conductance activation was possible only outside the physiological range of potentials. The time constant of Cl- conductance activation from closed to fully activated state was more than doubled following salt adaptation of the toads. The active inward Cl- flux disappeared in skins of toads adapted to a 250 mM-NaCl solution, and apparent leakage conductance was reduced. Application of the phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine to skin of fully salt-adapted toads increased the transepithelial Cl- conductance, and the time courses of voltage clamp currents became more like those of water-adapted toads. Apparent leakage conductance was increased.(ABSTRACT TRUNCATED AT 400 WORDS)

AB - The steady-state Cl- current across the skin of Bufo viridis adapted to tap water was found to be rectified. In skins bathed with NaCl Ringer on both sides, a large outward current, carried by influx of Cl-, was observed at a clamping voltage (V) of less than -50 mV (outside of the skin negative). for V = -50 mV the transepithelial Cl- conductance calculated from isotope flux measurements was 2.5 +/- 0.3 mS cm-2, N = 10. When the skin was clamped at + 50 mV the net flux of Cl- was reversed, but Cl- conductance was only 0.3 +/- 0.1 mScm-2. Flux ratio analysis indicated that the potential-activated Cl- conductance carries Cl- ions by way of passive transport. With NaCl Ringer bathing the outer surface of the skin the spontaneous potential was about -30 mV. At this potential the Cl- conductance of the skin was about half of its maximum value. The time course of Cl- current activation following a fast, stepwise change of V from 50 mV to a potential below O mV showed an initial delay of a few seconds, and proceeded with a halftime (T 1/2) which varied as a bell-shaped function of V. The maximum T 1/2 was about 100 s for V = -10 mV in skins exposed to KCl Ringer on the outside. Following adaptation of the toads to a 250 mM-NaCl solution, the fully activated Cl- conductance of the skin was greatly reduced, and the conductance-voltage curve was shifted to the left along the voltage-axis. With NaCl Ringer on the outside the spontaneous potential was about -20 mV, and Cl- conductance activation was possible only outside the physiological range of potentials. The time constant of Cl- conductance activation from closed to fully activated state was more than doubled following salt adaptation of the toads. The active inward Cl- flux disappeared in skins of toads adapted to a 250 mM-NaCl solution, and apparent leakage conductance was reduced. Application of the phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine to skin of fully salt-adapted toads increased the transepithelial Cl- conductance, and the time courses of voltage clamp currents became more like those of water-adapted toads. Apparent leakage conductance was increased.(ABSTRACT TRUNCATED AT 400 WORDS)

KW - Adaptation, Physiological

KW - Animals

KW - Bufonidae

KW - Chlorides

KW - Electrophysiology

KW - Female

KW - Male

KW - Skin

KW - Sodium Chloride

M3 - Journal article

C2 - 6736866

SN - 0022-0949

VL - 109

SP - 353

EP - 371

JO - Journal of Experimental Biology

JF - Journal of Experimental Biology

ER -