Fig. 1. Chelating extracellular Ca²⁺ increased osmotic fragility. The control was diluted amphibian Ringer solution (n=10), low Ca²⁺ was diluted Ringer containing 5 mM EGTA (n=10), and gramicidin (gram, 5 µM) was used in the presence of a low Ca²⁺ choline Ringer (n=10). Calcium ionophore A23187 (0.5 µM) was added to the control solution (n=10). Values are means±s.e.m. of optical density, obtained at concentrations of Ringer with approximately 50% lysed cells for the control. ^**P<0.01, ^***P<0.001.