...why high KCl depolarized the cells?

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Hss's picture
...why high KCl depolarized the cells?


In some protocols, for example calcium imaging, people use high KCl for induce some curents by depolarization. Can someone explain why high KCl extracellular application depolarized the cells? 


ps. It will be good to know too why NH4Cl extracellular application induced intracellular acidosis. I suppose this chemical give free H+ in the bath, and I wonder why the intracelluar pH changes. 

Bluejay's picture
My understanding is that the

My understanding is that the resting potential of most cells, i.e. about -70mV, is determined by the relative potassium levels inside and outside the cell, i.e. high potassium inside and 4mM in media or physiological salt solution, and thus controlled by the potassium channels.  Depolarization to bout 0mV? by adding high KCl to the cells is also used in Rubidium flux experiments in, for example, the hERG potasssium channel.  It is also used as a control when using membrane potential dyes.  For calcium, presumably high potassium opens voltage sensitive calcium channels, allowing calcium influx into the cells.  My frame of reference is neuronal cells.  Some cells, such as leukocytes, cannot be dopolarized with high KCl.