intake ECE ICF K+ K+ 3.5~5.5mmoL pump channe 140~160mmoL kidney Gi tract Direction oft shifting 90% Skin? Maintenance oft balanceDirection of K+ shifting 140~160mmol/L 3.5~ 5.5 mmol/L ECF ICF K+ K+ Maintenance of K+ balance intake kidney GI tract 90% Skin? 10% channel pump