AJP - Regulatory, Integrative and Comparative Physiology, Vol 273, Issue 3 991-R998, Copyright © 1997 by American Physiological Society

ARTICLES

K(+)-Cl- cotransport and volume regulation in the light and the dense fraction of high-K+ dog red blood cells

H. Fujise, K. Abe, M. Kamimura and H. Ochiai
Second Department of Pathology (Pathobiochemistry), School of Veterinary Medicine, Azabu University, Kanagawa, Japan.

We examined a chloride (Cl-)-dependent K+ transport (K(+)-Cl- cotransport) and regulatory volume decrease in dog red blood cells with high K+, low Na+, and high glutathione (GSH) content (HK/HG) due to the presence of an Na(+)-K+ pump. The HK/HG cells were separated according to their density, and the age-marker enzyme activities, such as glucose-6-phosphate dehydrogenase and cholinesterase, were determined. Unexpectedly, we found that young cells were heavier (more dense) and smaller in size compared with the old cells, which were lighter (less dense) and larger. The K(+)-Cl- cotransport was nearly 10-fold higher in the most dense cells, representing a 12% fraction of the total population compared with the lightest cohort. Although K(+)-Cl- cotransport in both the dense and the light cells was activated by N-ethylmaleimide, swelling and depletion of cellular divalent cations and the activation of the transport in the dense cells was greater. Both the dense and light cells regulated their volume when they were isosmotically swollen. Therefore, the lower activity of K(+)-Cl- cotransport might not explain the relative large volume in old HK/HG cells. The concentration of GSH and glutamate was higher in the light cells. Thus the higher the GSH and glutamate concentration, the greater the cell volume and the lower the K(+)-Cl- cotransport.

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