Estradiol receptor activity in lyophilized calf uterus and human breast tumor tissue

Estradiol receptors (ER) were analyzed in lyophilized human breast tumor specimen and in calf uterus tissue by a dextran-coated charcoal method. No decline of ER occurred when lyophilized calf uterus tissue was stored for six to eight months at 0-4 C and for two weeks at room temperature. During storage of lyophilized human breast tumor tissue for several months at 0-4 C and for four weeks at room temperature, no or only a minor decrease of ER binding sites was observed. Therefore, it is recommended to use lyophilized target tissues for intra- as well as interlaboratory quality control studies of steroid receptor measurements.