TY - JOUR
T1 - Ion transport and permeability in the mouse egg
AU - Powers, R. D.
AU - Tupper, J. T.
N1 - Funding Information:
This work was supported by grants from the American Cancer Society and the Syracuse University Educational ImprovementP rogram.
PY - 1975/3/15
Y1 - 1975/3/15
N2 - Sodium, potassium, and chloride unidirectional fluxes have been studied in the mature mouse egg. Their relationship to cell membrane potential and conductance has been investigated. Unidirectional Na efflux is composed of a ouabain sensitive component, presumably representing an active Na efflux, an external Na-dependent component and a diffusional component. The data indicate that the external Na-dependent component represents a Na:Na exchange mechanism. There also exists an ouabain-sensitive component of K influx. The stoichiometry of the ouabain-sensitive fluxes is approx. 2.7:1 (Na to K). From the diffusional components of Na and K flux, the membrane permeability to these cations has been estimated. PNa and PK are 1.2 × 10-7 cm sec-1 and 0.8 × 10-7 cm sec-1 respectively. These permeabilities, in conjunction with the internal exchangeable fractions of Na and K and the external concentrations, predict an egg membrane potential of -11 mV (inside negative). Microelectrode measurements yield an egg membrane potential of -14 ± 0.4 mV, indicating that the cell membrane potential is predominantly a result of the Na and K permeabilities and distributions. Internal exchangeable Cl is 67 ± 3 mM in standard medium, as determined from 36Cl distribution. The chloride equilibrium potential is therefore -15 mV, which is not significantly different from the egg membrane potential. This suggests that Cl distributes passively across the egg membrane, reflecting the egg membrane potential. Hyperpolarization of the egg membrane potential to -27 ± 1.5 mV by reduction of external Na results in an exchangeable internal Cl of 49 ± 8 mM. This yields a Cl equilibrium potential of -24 mV, indicating that the Cl distribution shifts in the predicted manner upon a change in cell membrane potential. Tracer flux data indicate that Cl conductance comprises the bulk of the total membrane conductance with Na and K sharing the remainder in approximately equal amounts.
AB - Sodium, potassium, and chloride unidirectional fluxes have been studied in the mature mouse egg. Their relationship to cell membrane potential and conductance has been investigated. Unidirectional Na efflux is composed of a ouabain sensitive component, presumably representing an active Na efflux, an external Na-dependent component and a diffusional component. The data indicate that the external Na-dependent component represents a Na:Na exchange mechanism. There also exists an ouabain-sensitive component of K influx. The stoichiometry of the ouabain-sensitive fluxes is approx. 2.7:1 (Na to K). From the diffusional components of Na and K flux, the membrane permeability to these cations has been estimated. PNa and PK are 1.2 × 10-7 cm sec-1 and 0.8 × 10-7 cm sec-1 respectively. These permeabilities, in conjunction with the internal exchangeable fractions of Na and K and the external concentrations, predict an egg membrane potential of -11 mV (inside negative). Microelectrode measurements yield an egg membrane potential of -14 ± 0.4 mV, indicating that the cell membrane potential is predominantly a result of the Na and K permeabilities and distributions. Internal exchangeable Cl is 67 ± 3 mM in standard medium, as determined from 36Cl distribution. The chloride equilibrium potential is therefore -15 mV, which is not significantly different from the egg membrane potential. This suggests that Cl distributes passively across the egg membrane, reflecting the egg membrane potential. Hyperpolarization of the egg membrane potential to -27 ± 1.5 mV by reduction of external Na results in an exchangeable internal Cl of 49 ± 8 mM. This yields a Cl equilibrium potential of -24 mV, indicating that the Cl distribution shifts in the predicted manner upon a change in cell membrane potential. Tracer flux data indicate that Cl conductance comprises the bulk of the total membrane conductance with Na and K sharing the remainder in approximately equal amounts.
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U2 - 10.1016/0014-4827(75)90122-6
DO - 10.1016/0014-4827(75)90122-6
M3 - Article
C2 - 1168582
AN - SCOPUS:0016823575
SN - 0014-4827
VL - 91
SP - 413
EP - 421
JO - Experimental Cell Research
JF - Experimental Cell Research
IS - 2
ER -