Pressure jump relaxation kinetics of frog skin open circuit voltage and short circuit current.

The relaxation kinetics of frog skin open circuit voltage, Voc, and short circuit current, Isc, was studied by analyzing the effects of subjecting the tissue to sudden increments of hydrostatic pressure. Both Voc and Isc are perturbed by the pressure jump. Changes in Voc can be resolved into three components: a rapid decrease (phase I), a second, additional decrease with time constant 2.2 s (phase II), and finally a very slow increase found only in some preparations. The amplitudes of phases I and II are linear in the range of pressures studied (less than 350 atm) and have respective pressure coefficients of -1.2.10(-4) atm-1 and 3.7.10(-4) atm-1. Under short circuit conditions, phases I and II persist. The pressure coefficients of the amplitudes of phases I and II, -4.3.10(-4) ATM-1 and -5.0.10(-4)ATM-1, respectively, are larger than those of Voc, but the time constant of phase II, 2.2 S, is the same. The sum of the amplitudes of phases I and II is directly proportional to Isc when it is inhibited with ouabain. It is argued that in both electrical states pressure perturbs the same transport mechanism giving rise to phases I and II of Voc and of Isc. The magnitude of the pressure coefficients of these processes implies that they arise from chemical reactions, rather than from simple, physical solution properties. Comparison of the pressure jump kinetics with the previous spectral analysis of the electrical fluctuations of frog skin suggests a common origin for both sets of phenomena.