The suction capillary contained another small capillary (0.5 mm diameter tip) in the central part filled with Corning Code No 477317 liquid ion-exchanger (Dow Corning Corporation, Midland, Michigan, USA) for conventional measurement of a0K . The reference channel (suction capillary) was filled with conventional Ringer’s solution (0.1 mL). Electrodes were connected by Ag/AgCl wires to the input of a high impedance (10 MQ) direct current amplifier with a negative input capacity compensation . Electrical resistance of the ion-selective channel of the potassium-sensitive electrodes was usually between 170 to 200 MQ and the time constant 3 to 5 ms. Electrodes were calibrated before and after each experiment with solutions containing K+ 5, 10, 15 and 20 mmol/L and with 100 mmol/L of Na+ as background, both under normal atmospheric pressure and during application of negative pressure to exclude the possibility of dilution of the Ringer’s solution in the suction electrode. a0K did not change during calibration of the electrode under negative pressure, which lasted 5 mins. It was estimated from the potential difference (Vdif) between the extracellular potassium-sensitive electrode and an extracellular reference electrode (Vref) placed in Ringer’s solution (comprising [in mmol/L] Na+ 102.0, K+ 5.6, Ca2+ 1.8, Cl- 111.2, NaHCO3- 1.0) in the suction electrode. An activity coefficient of 0.746 was assumed in order to evaluate voltages reflecting a0K . Dreaming of a reliable pharmacy to find birth control for women and spend less money?