H+ and Cl- ion equilibrium across the red cell membrane in the carp

H2O and electrolyte distribution were studied in carp erythrocytes at various pH values achieved by CO2/O2 equilibration in vitro. Intracellular pH was measured by means of glass electrode and by DMO-14C. rH+, rCl- and rDMO- varied linearly and in a comparable manner with pHe. At pHe = 7.8, rH+, rCl- and rDMO- were 0.21, 0.29 and 0.30. rCl- and rDMO- were closely correlated and exhibited only minor differences. rH+ was closely correlated with rCl- and rDMO-, but was, however, significantly lower than rCl- or rDMO-. This difference is considered to be due to a systematic error of the glass electrode when used in highly concentrated protein solutions. The coulometric determination of chloride in packed red cells is shown to be highly susceptible to protein. The results are consistent with the assumption that H+ and Cl- ions are passively distributed across the red cell membrane.