Abstract
After massive hemorrhage, adult sheep with genotypically low potassium (LK) red cells temporarily produce high potassium (HK) cells with ouabain-sensitive K+ pump fluxes equivalent to mature HK red cells. In light of recent reports of different red cell volume populations accompanying the HK-LK transition also occurring in newborn LK sheep and the unresolved controversy over the effect of anti-L on K+ transport in these immature red cells, we have reexamined the K+ transport changes and the effect of anti-L in the newly formed HK cells at various times after anemic stress and under in vitro conditions. We found that approximately 7 d after bleeding, maximum reticulocytosis occurred in the peripheral blood. After separation by density centrifugation, the top 10% cell fraction contained 100% reticulocytes, with a mean cell volume 2.5 times larger than that of mature erythrocytes. These immature red cells were of HK type, and their K+ pump and leak fluxes were 30 and 10 times higher, respectively, than those found in mature LK cells. The new cells may possess HK- and LK-type pumps because K+ pump influx was significantly stimulated by anti-L. When separated by density centrifugation on days 9, 17, and 23 after bleeding, some of the cells apparently maintained their large size while gaining higher density. Large cells from day 9, kept in vitro for 22 h, showed anti-L-sensitive K+ pump and leak fluxes that declined within hours, paralleling the behavior of these cells in vivo, whereas cellular K+ levels changed much less. It is concluded that the newly formed red cells may belong to a stress-induced macrocytic cell population that does not acquire all of the characteristics of adult LK cells.
Highlights
Lee et ai. (1966) have reported that adult sheep with genotypically low potassium (LK) red cells, when subjected to massive hemorrhage, temporarily produce immature red cells of high potassium (HK) type
The results presented provide some new insight into the LK-HK-LK transition that occurs in the red cells of massively bled LK sheep
In response to an acute anemic stress, the following physiological events defined the emergency recovery phase. (a) Large immature cells, 2.5 times the normal mature red cells, were released into the circulation. Some of these cells appeared to sustain their large size while gaining greater density in the course of cellular maturation spanning a few days. (b) The new cells had a high K + concentration of nearly 80 mmol per liter of cells, with 30 and 10 times higher K § pump and leak fluxes, respectively
Summary
Lee et ai. (1966) have reported that adult sheep with genotypically low potassium (LK) red cells, when subjected to massive hemorrhage, temporarily produce immature red cells of high potassium (HK) type. (1966) have reported that adult sheep with genotypically low potassium (LK) red cells, when subjected to massive hemorrhage, temporarily produce immature red cells of high potassium (HK) type. Active K + transport was fourfold to fivefold higher in the newly formed cells, whereas the ouabaininsensitive K + leak flux was only slightly larger. Rockefeller University Press , 0 0 2 2 - 1 2 9 5 / 8 0 / 0 7 / 0 1 0 9 / 1 3 5 1 . THE JOURNAL OF GENERAL PHYSIOLOGY - VOLUME 76 9 1980 immature cells only temporarily retain their H K characteristics before joining the pool of mature LK red cells. The HK-LK [ransition was considered to be a result of modification of membrane transport properties in the circulating immature red cells
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