Changes in intracellular calcium and in membrane currents evoked by injection of inositol trisphosphate into Xenopus oocytes

Abstract

Intracellular calcium was monitored by the use of aequorin in voltage-clamped oocytes of Xenopus laevis. Injection of inositol trisphosphate (IP$_{3}$) into oocytes elicited slowly rising and decaying aequorin/calcium signals and produced oscillatory chloride membrane currents. These responses did not depend upon extracellular calcium, since they could be elicited in calcium-free solution and after addition of cobalt or lanthanum to block calcium channels in the surface membrane. We conclude that IP$_{3}$ causes the release of calcium from intracellular stores in the oocyte. Injections of calcium gave aequorin and membrane current responses that were more transient than those seen with IP$_{3}$.