Relationship of depolarization to phosphorus metabolism and transport in excitable tissues

Abstract

In the presence of Ringer solution containing a high concentration of potassium ions, the incorporation of orthophosphate-P32 into ATP and other organophosphates of the desheathed sciatic nerve or spinal ganglia of bullfrog was inhibited over 75%. The inhibition in calcium-free Ringer solution containing EDTA was somewhat less. With increasing external K+ there was a good correlation between the decrease in the resting potential of spinal ganglion cells and the inhibition of P32 incorporation into ATP and phosphocreatine. Since oxidative phosphorylation or carbohydrate metabolism was not inhibited by high K+, it was concluded that the K+ interfered with the transport mechanisms involved in orthophosphate-P32 exchange across the nerve membrane. Pi transport was believed to involve the following three chain-linked reactions: 1) carrier + P ⇌ carrier P; 2) carrier P ⇌ carrier + Pi; 3) Pi + ADP ⇌ ATP, where the first two reactions occurred in the membrane and the third within mitochondria. Reaction I or II was presumed to be K+ sensitive. The possible mechanisms involved in such an inhibition are discussed in terms of present-day theories relating to bioelectric phenomena.