The development of an active transport system for potassium in the embryonic avian erythrocyte

Abstract

Measurements were made of water, Na, and K content of the albumin, yolk, subembryonic liquid, and whole blastula of the chick 24 hr after fertilization. The close similarity of cell Na and K concentrations to those of the subembryonic liquid (Na, 22:27; K, 24:31) and the absence of ouabain-inhibitable uptake of 42 K by the blastula suggested that cells and subembryonic liquid were in diffusion equilibrium. The loss of virtually all nonerythrocyte cells upon the transfer of the deembryonated blastula to a culture medium allows investigation for evidence of development of an Na:K pump in the erythrocyte. At 24 hr the cultured cells maintained cation gradients of 40:140 mequiv/liter for Na and 49:5 mequiv/liter for K. At 48 hr the figures were 33:140 mequiv/liter for Na and 58:5 mequiv/liter for K. The cells cultured for 24 hr took up 13.4% of available 42 K without ouabain and 2.8% with 10 −5 M ouabain, ( P < 0.001). At 48 hr the cells took up 14.2% of 42 K without ouabain and 4.9% with ouabain ( P < 0.001). It appears that no cell in the chick blastula can transport K actively at 24 hr, but 48 hr after fertilization an active transport mechanism can be identified which can create and maintain transmembrane K gradients.