quality control in steroid hormone receptor analyses.

In this paper, standards for steroid hormone receptor determinations in cancer tissue have been outlined. Standardization of methods for receptor extraction and receptor assay are equally important; and it is a condition sine qua non, if comparable receptor values between different centers for multilocal studies are required. Immediate and proper cooling of the tissue samples after removal, homogenization at the temperatures of the liquid nitrogen (as well as the presence of a sulfhydryl-protecting agent in the extraction medium), and the use of a simple, reproducible assay procedure are most important. As a standard procedure for ER- and PR-assays, the charcoal adsorption method combined with a scatchard-plot has been suggested. Reference procedures, like protein with DNA-assays, must also be standardized. Quality control experiments can be performed with lyophylized calf uterus homogenates. Additional determination of the nuclear estradiol in the high-speed sediments by radioimmunoassay is highly recommended.