Premium
The partition of sodium fluxes in isolated toad oocytes
Author(s) -
Dick D. A. T.,
Lea E. J. A.
Publication year - 1967
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1967.sp008251
Subject(s) - toad , sodium , partition (number theory) , chemistry , medicine , biophysics , endocrinology , biology , mathematics , combinatorics , organic chemistry
1. The rate constant for Na efflux from the oocyte calculated from (d/d t ) (ln [Na * ] i ]) is only approximately 52% of that calculated from (d/d t )[(ln(d[Na * ] i )d t )]. The difference may be interpreted by supposing that 48% of the internal Na of the oocyte is either bound to proteins or sequestered in cell organelles. 2. The mean rate constant for Na efflux was 6·4 × 10 −3 min −1 corresponding to an apparent Na efflux rate of 13·3 p‐mole/cm 2 .sec. When this is corrected for the increase in surface area produced by microvilli the true efflux rate is 1·1‐1·3 p‐mole/cm 2 .sec. 3. The action of ouabain (1‐5 μ M ) appears to involve two different effects: ( a ) there is 48‐65% inhibition of the membrane Na pump, and ( b ) there is a release of some of the sequestered Na in the cell. 4. Removal of external K causes a 40% reduction in Na efflux although this value may be an underestimation owing to the presence of K which has leaked from the cell and may be retained near the cell surface. 5. Raising the external K concentration to 15 m M reduces the inhibitory effect of ouabain by approximately a half. 6. It was concluded that the Na pump in the toad oocyte may have a slightly lower level of activity than that in frog muscle, but that its general properties are similar to those in frog muscle and some other animal cells.