Amiloride-sensitive components of sodium transport in guinea pig red blood cells: A cause of imbalance of sodium ion at low temperature
Zhao, Zhihong
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Permalink
https://hdl.handle.net/2142/23552
Description
Title
Amiloride-sensitive components of sodium transport in guinea pig red blood cells: A cause of imbalance of sodium ion at low temperature
Author(s)
Zhao, Zhihong
Issue Date
1991
Doctoral Committee Chair(s)
Willis, John S.
Department of Study
Biology, Animal Physiology
Biology, Zoology
Discipline
Biology, Animal Physiology
Biology, Zoology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Animal Physiology
Biology, Zoology
Language
eng
Abstract
It has previously been found that gaining of Na in red cells of guinea pig is faster than in those of ground squirrel during cold storage at 5$\sp\circ$C in vitro and amiloride can partially inhibit the accumulation. Also, amiloride-sensitive Na influx in guinea pig red cells is known to be larger at 20$\sp\circ$C than at 37$\sp\circ$C.
In this study, it is shown that amiloride-sensitive Na influx in guinea pig red blood cells can be activated by cytoplasmic H$\sp+$ and it is correlated with cation-dependent H$\sp+$ loss from acidified cells. It is also stimulated by shrinkage and by phorbol ester in the presence of Ca, as is Na-H exchange in other cells. Aside from this apparent Na-H exchange, there are at least one and possibly two other distinct components of amiloride-sensitive Na influx: one is hypertonically induced, with a high sensitivity to amiloride and with low sensitivity to Na; the other appears to represent Na-Mg exchange.
Comparison between results at 37$\sp\circ$C and 20$\sp\circ$C shows that amiloride-sensitive Na influx can be activated dramatically by the activators of Na-H exchange at 37$\sp\circ$C, but not at 20$\sp\circ$C. Cell alkalinization can diminish the elevation of amiloride-sensitive Na influx at 20$\sp\circ$C, while depletion of cell magnesium can not. These observations lead to the conclusion that cooling-induced amiloride-sensitive Na influx in guinea pig cells is mainly due to the increased activity of the Na-H exchange mechanism.
"By measurement of the stimulation of amiloride-sensitive Na influx by cytoplasmic H$\sp+,$ the affinity of the amiloride-sensitive Na-H exchanger to cytoplasmic H$\sp+$ is found to be higher at 20$\sp\circ$C than at 37$\sp\circ$C. In cells incubated in Na-free medium at 37$\sp\circ$C (""reversed Na gradient""), acidification increased amiloride-sensitive Na efflux, indicating the presence of a cytoplasmic regulatory site for H$\sp+.$ At 20$\sp\circ$C, acidification caused no significant increase, but basification inhibited Na efflux into Na-free medium, indicating higher sensitivity of the regulatory site to cytoplasmic H$\sp+.$ Thus increased activity of the Na-H exchange at reduced temperature is characterized by reduced H$\sp+$ transport but increased affinity of a regulatory site for H$\sp+.$"
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