Calcium and potassium uptake from sodium free media by frog stomach muscle.

Abstract

Summary and ConclusionsIsolated strips of frog stomach muscle, previously immersed overnight at 5°C in Na+ free Ringer solutions containing 110 mEq Li+, 6 mEq K+, and 1.8 mEq Ca++/1 accumulated K+ when reimmersed in a solution containing 106 mEq Na+, 10 mEq K+ and 1.8 mEq Ca++/1. When Na+ was replaced by Li+ in the second immersion fluid, K+ accumulation was inhibited. Removal of Ca++ from the Li+ Ringer used for the second immersion did not significantly increase the uptake of K+ by the fibers. Muscles kept in Ca++ free Li+ Ringer during both immersions had a significantly lower K+ content than muscles immersed throughout in Li+ Ringer containing 1.8 mM Ca+ + . Increasing the Ca++ content of the fluid used for the second or for both immersions had no significant effect on the final K+ content of muscles kept throughout the experiment in media containing normal concentrations of Na+. It is concluded that the inhibition of K+ uptake by frog stomach muscle observed when Na+ is replaced by Li+ in the second ...