Polarization variations induced by high hydrostatic pressures in the isolated frog skin as related to the effects on passive ionic permeability and active Na+ transport

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Abstract
The effects of a wide range of hydrostatic pressures (from 50 to 1000 kg/cm2) have been investigated on the spontaneous potential difference (PD), the short-circuit current (SCC) and the activity of the membrane ATPases of the isolated abdominal skin from the frog Rana temporaria L. Two types of variations in PD are induced by pressure changes: short and transient potential variations which appear to be related to the pressure change (compression and decompression) and lasting variations which persist as long as pressure is applied and whose nature appears to be related to the pressure magnitude. Long-lasting potential changes have particularly been investigated. At pressures lower than 500 kg/cm2, the skin potential increases while a pressure over 500–600 kg/cm2 induces a depolarization. Both variations consecutively occur at 500 + 100 kg/cm2. These effects of pressure have been shown to be reversible up to about 800 kg/cm2. The question of the origin of the potential changes is discussed and it is proposed that the lasting hyperpolarization results from an effect on the passive permeabilities to Na+, K+ and Cl- ions inducing in turm a secondary readjustment (stimulation) of the Na+ active transport while the depolarization at high pressures reflects a direct inhibition of the Na+ pump. These interpretations are supported by experimental data on the effects of pressure on the short-circuit current and on the activity of the skin (Na+ + K+) ATPase.