J. Biol. Chem., Vol. 260, Issue 6, 3337-3343, Mar, 1985
(Na,K)-ATPase and Ouabain binding in reticulocytes from dogs with high K and low K erythrocytes and their changes during maturation
Y Maede and M Inaba
The present study demonstrated that dog reticulocytes had considerable
amounts of (Na,K)-ATPase, but lost it rapidly during maturation into
erythrocytes. Furthermore, reticulocytes from dogs possessing erythrocytes
characterized with high (Na,K)-ATPase activity and high K, low Na
concentrations (HK dogs; Maede, Y., Inaba, M., and Taniguchi, N. (1983)
Blood 61,493-499) had more ouabain binding sites than cells from normal
dogs (LK dogs). Our results were as follows: i) The maximal binding
capacities (Bmax) for ouabain binding at equilibrium were approximately 0
and 1,500 binding sites/cell in LK and HK dog erythrocytes, respectively.
ii) Reticulocytes from LK dogs possess approximately 5,700 ouabain binding
sites/cell. iii) The Bmax value for ouabain in HK reticulocytes was about
10,000 sites/cell, being 2-fold that in LK reticulocytes. iv)
Ouabain-sensitive fluxes of 24Na and 42K in each type of reticulocyte were
compatible with the number of ouabain binding sites on the cells. v)
Ouabain binding capacity, as well as (Na,K)-ATPase activity, in the
reticulocytes from LK dogs fell rapidly to nearly zero during the
maturation into erythrocytes. vi) Although reticulocytes from HK dogs also
showed a similar regression of (Na,K)- ATPase during maturation, they
retained a certain number of ouabain binding sites even after maturation,
resulting in the high activity of (Na,K)-ATPase in HK erythrocyte membrane.