The use of coated charcoal in the determination of oestrogen receptor activity.

Oestrogen receptor activity in mammary tumour and healthy tissues were determined by using a method of incubation with coated charcoal. It appears that both increased charcoal concentration and prolonged incubation leads to erroneous results, which are probably due to loss of receptor protein. It is concluded that receptor activity assays must be performed under strictly standardized experimental conditions.