SPECIFIC BINDING OF [3H]OESTRADIOL BY CYTOPLASMIC PROTEIN COMPONENTS OF FEMALE RAT LIVER

Abstract

Department of Neurology, Hadassah University Hospital, Jerusalem, Israel (Received 27 October 1975) Several criteria have been established for those proteins of fundamental importance in the mechanism of steroid hormone action as opposed to those, essentially transport proteins, which are unable to elicit a biological effect when associated with steroid. Receptor proteins found in target cells may be characterized by their restricted concentration but high affinity for steroid, together with high ligand and tissue specificity (Baulieu, Raynaud & Milgrom, 1970). In studies designed to show the organ specificity of the receptor for oestradiol in mammary tumours induced by 7,12-dimethylbenz [a] anthracene in the female rat (Powell-Jones, Jenner, Blarney, Davies & Griffiths, 1975), the presence in liver cytosol fractions of protein components specifically retaining oestradiol with high affinity but low capacity was demonstrated. Fig. 1. Cytosols were prepared from liver tissue of a mammary tumour-bearing rat (cytosol protein 17 mg/ml) and from