Abstract
1. An ATPase activity relating to the active transport of Na+ and K+ in the cortex of the sea urchin egg was detected.
2. The activity was maximum at the pH and the ionic strength of ordinary sea water.
3. The activity required the presence of both Na+ and K+, but it was inhibited by ouabain, metabolic inhibitors and detergent.
The author expresses his sincere gratitude to Prof. R. Ito and Dr. Y. Ito of the Department of Physiology, School of Medicine, and Prof. F. Oosawa of the Institute for Molecular Biology, of Nagoya University for their valuable suggestions. He is also indebted to Prof. M. Sugiyama and Dr. M. Ishikawa of the Sugashima Marine Biological Station, Drs. R. Hori of Toyama University and H. Sakai of Tokyo Metropolitan University, for their kind help during the experiment.
