Concentration dependence of active potassium transport in the human red blood cell in the presence of inhibitors

The active potassium influx in the human red blood cell is inhibited by strophanthidin, ethacrynic acid, and MK-870 (a new diuretic), and the degree of inhibition is greater at low concentrations of extracellular potassium than at high. In the case of ethacrynic acid, potassium appears to diminish the rate of combination of the drug with the transport system. The kinetic behavior of the active potassium influx in the presence of the inhibitors strophanthidin and ethacrynic acid is consistent with a model in which the binding of potassium at one of the potassium-sensitive sites in the transport system reduces the affinity of the system for the drug, and binding of a second potassium ion further reduces the affinity. It is not possible to distinguish between the sites on the basis of the studies presented here.

 

Comments：

The passage describes the effects of several compounds on the active potassium influx in human red blood cells. Strophanthidin, ethacrynic acid, and MK-870 are all inhibitors of this influx, with greater inhibition at low extracellular potassium concentrations. The interaction of ethacrynic acid with the transport system is affected by potassium, with the drug combining more slowly with the system in the presence of potassium.

The behavior of the transport system in the presence of strophanthidin and ethacrynic acid is consistent with a model in which the system has two potassium-sensitive sites. Binding of potassium to the first site reduces the affinity of the system for the drug, and binding of a second potassium ion further reduces the affinity. However, the studies presented in the passage do not provide enough information to distinguish between these sites.

Overall, the passage provides information on the effects of various compounds on the active potassium influx in human red blood cells and suggests a model for the behavior of the transport system in the presence of these compounds and potassium ions.

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