Ion homeostasis and energy loss in the anoxic frog brain (Rana pipiens)

This study investigated the homeostasis of extracellular potassium ion concentration ([K+]e) and correlated energy levels in the anoxic frog brain (Rana pipiens). The results showed K+ ion homeostasis was maintained for 3hrs in anoxia. It confirmed a constant decline in brain ATP in anoxia. It was concluded that ion homeostasis in the frog does not rely on the maintenance of normoxic levels of ATP. When Na+/K+ATPase was inhibited, it was found that initial K+ efflux was decreased in the anoxic frog. This could be due to decreased ion permeability in anoxia, an adaptive strategy seen in other anoxic tolerant organisms. However, the study showed once a threshold [K+]e was reached, the final K + efflux pattern was unchanged. This [K+]e appears to represent a membrane potential threshold. Critical energy levels were determined representing the energy minimum to maintain ion homeostasis in the anoxic frog brain.