Characteristics of the inwardly-rectifying time-dependent currents in mytilus hemocytes.

<p>A) Voltage protocol applied to <i>M</i>. <i>galloprovincialis</i> hemocytes eliciting time-dependent currents. The duration of the main pulse was 5 s and the applied voltages ranged from +50 mV up to –120 mV in –10 mV decrements. B) Typical whole-cell inwardly rectifying time-dependent currents that activate slowly on the application of the hyperpolarizing pulses represented in A and deactivate in a fraction of seconds after the voltage repolarization to positive values. Holding and tail membrane potentials were +40 mV and -50 mV, respectively. Experiments performed in the hyposmotic bath solution with osmolality equal to 897 mosmol/kg. C) Values of the normalized currents (I_Norm) obtained mediating the final segment of each steady-state current from at least 4 different experiments. The data were normalized with respect to the absolute value of the current at V = -110 mV and plotted as a function of the applied transmembrane potential. D) Filled symbols represent G_Norm in hyposmotic solutions plotted as a function of the membrane potential; the solid line represents the best fit of the experimental data by the Boltzmann equation. Interestingly, in the same set of cells, a comparison of the Boltzmann distributions was left-shifted towards more negative membrane potentials by as much as -44.9 ± 4.4 mV when the hyposmotic solution (filled circles) bathing the cell was replaced by an identical hyperosmotic solution (empty symbols at ∏ = 1178 mosmol/kg), thus implying that more negative membrane potentials are needed to activate the same current at higher osmolality. V_1/2<i>(hypo)</i> = -37.2 ± 1.3 mV and V_1/2<i>(hyper)</i> = -82.1± 3.1 mV, z<i>(hypo)</i> = 1.8± 0.1 and (z<i>(hyper)</i> = 1.7±0.1).