Enhanced Ca2+ uptake and ATPase activity of sarcoplasmic reticulum in the presence of diethyl ether.

The presence of diethyl ether enhances the rates of both Ca2+ uptake and ATPase activity in sarcoplasmic reticulum vesicles (SR) isolated from rabbit skeletal muscle. Stopped-flow measurements of Ca2+ transport in SR show that, in the absence of oxalate and other calcium-complexing anions, the initial velocity of the ATP-dependent Ca2+ uptake increases from 60 to 107 nmol of Ca2+/s/mg of protein when 5% (v/v) diethyl ether is present. Similar concentrations of diethyl ether increase steady state levels of Ca2+ accumulation by over 80%. Parallel to the enhancement of the rate of Ca2+ transport, diethyl ether induces an increased rate of Ca2+-dependent ATPase activity. Among four other ether compounds tested, three enhanced the rate of Ca2+ uptake, but none as effectively as diethyl ether, and a fourth reduced the rate of Ca2+ transport by the SR. These results contrast with previous observations concerning the effect of diethyl ether on ATP-dependent Ca2+ transport by SR and are now consistent with a direct pharmacological action of ether as a muscle relaxant at the level of SR Ca2+ transport.