A simple method for measuring total calcium in small tissue samples

A simple and accurate method for determining total calcium in small tissue samples using aequorin is described. The method involves measuring the calcium-induced luminescence of aequorin with the tritium channel of a liquid scintillation counter. The sensitivity of the method and specificity of the method for calcium have been determined and, theoretically, this method could determine calcium in tissue samples weighing 3 mg or as little as 2 nmol of calcium could be measured.