The Reponse of Duck Erythrocytes to Norepinephrine and an Elevated Extracellular Potassium : Volume regulation in isotonic media

This paper presents evidence that duck erythrocytes regulate their size in isotonic media by utilizing a previously reported "volume-controlling mechanism." Two different experimental situations are examined. In the first, cells enlarge in a solution containing norepinephrine and an elevated [K]_o; and in the second, enlarged cells shrink to their original size if the norepinephrine and excess potassium are removed. As the erythrocytes enlarge, K, Cl, and H₂O accumulate. Shrinkage, in contrast, is accompanied by the controlled loss of K, Cl, and H₂O. These changes and the associated changes in membrane permeability resemble those reported previously when duck erythrocytes incubate in anisotonic media. There cells, after first shrinking or swelling, utilize a "volume-controlling mechanism" to reestablish their original size. The mechanism regulates cell size by adjusting the total number of osmotically active intracellular particles. The present studies indicate duck red cells use this mechanism to readjust their total monovalent cation content and thus their solute content in isotonic media as well. In addition, evidence is presented which indicates that the "volume-controlling mechanism" and ouabain-inhibitable cation pump differ functionally.