The Response of Duck Erythrocytes to Nonhemolytic Hypotonic Media

Abstract

Duck erythrocytes were incubated in hypotonic media at tonicities which do not produce hemolysis. The cells' response can be divided into two phases: an initial rapid phase of osmotic swelling and a second more prolonged phase (volume regulatory phase) in which the cells shrink until they approach their initial isotonic volume. Shrinkage associated with the volume regulatory phase is the consequence of a nearly isosmotic loss of KCI and water from the cell. The potassium loss results from a transient increase in K efflux. There is also a small reduction in Na permeability. Changes in cell size during the volume regulatory phase are not altered by 10 -4 M ouabain although this concentration of ouabain does change the cellular cation content. The over-all response of duck erythrocytes is considered as an example of "isosmotic intracellular regulation," a term used to describe a form of volume regulation common to euryhaline invertebrates which is achieved by adjusting the number of effective intracellular osmotic particles. The volume regulatory phase is discussed as the product of a membrane mechanism which is sensitive to some parameter associated with cell volume and is capable of regulating the loss of potassium from the cell. This mechanism is able to regulate cell size when the Na-K exchange, ouabain-inhibitable pump mechanism is blocked.

Regulation of Cytoplasmic and Vacuolar Volumes by Plant Cells in Suspension Culture

“…Sutton-Jones and Street (28) also showed that in cell suspensions ofAcerpseudoplatanus the cytoplasm reaches its maximum thickness in the early stages of the cell division phase, but they gave no quantitative data. In the present culture, cells on a 7-day cycle never become highly vacuolated, but if the culture is continued for a longer time, the vacuole volume reached 90%7b of the cell volume by day 12 ( Fig. 3).…”

“…For instance, it has been suggested that the volume of wallless cells may be sensed by the tension of the plasma membrane (11,12), but this concept is less simple in vacuolate cells, where the tension of the tonoplast presumably depends more on the volume ofthe vacuole than on the volume ofcytoplasm. Moreover, current concepts of volume regulation focus on adaptation to environmental changes, but largely ignore the question of how the cytoplasmic volume keeps pace with other cellular growth processes.…”

Functional Separation of the Na-K Exchange Pump from the Volume Controlling Mechanism in Enlarged Duck Red Cells

“…The procedures for obtaining LSS cells ([K], 110 mmol/liter, [Na], -5 mmol/liter, and [Cl], 51 mmol/liter) has been described elsewhere (1,2).…”

“…1 in reference [1]). This same reference (1) also contains a description of the procedures for measuring the rate of 24 Na and 42K loss from cells.…”

“…Duck erythrocytes can readjust their size by utilizing a ouabain-insensitive "volume controlling mechanism" (1,2). This mechanism regulates the cation content of cells; the changes in cation content produce, in turn, isosmotic shifts in cell water and changes in cell size (3).…”