Effect of gamma-thio-ATP on dog stomach smooth muscle membranes

The effect of gamma-Thio-ATP on high affinity ATPase and on the ATP-dependent Ca-uptake of a plasma membrane fraction prepared from the dog stomach smooth muscle was examined. gamma-Thio-ATP did not act as a substrate for the ATP-dependent Ca-uptake and was only a poor substrate for the high affinity Ca-ATPase reaction. The compound, however, reversibly inhibited the uptake and the ATPase.