Androgen-binding proteins in sheep epididymis: characterization of a cytoplasmic androgen receptor in the ram epididymis

Abstract

ABSTRACT An androgen receptor (Rc) was demonstrated in caput, corpus and cauda epididymal cytosols of the ram. This receptor had a high affinity for 5α-dihydrotestosterone (Kd = 5·2 × 10−9 mol/l) and could be distinguished from the androgen-binding protein (ABP) by several characteristics. On polyacrylamidegel electrophoresis, Rc had a mobility of 0·37 and ABP 0·61; Rc sedimented in the 9S region of a linear sucrose gradient whereas ABP migrated in the 4·3S region; the molecular weights were 192 000 and 90 000 for Rc and ABP; their isoelectric points were 5·7 and 4·8–5·0; they were proteinaceous components since they were destroyed by proteolytic enzymes and heating (50 °C for Rc and 60 °C for ABP); they exhibited different half-times of dissociation: 20 h at 0 °C for Rc and 6 min for ABP, which is in agreement with their respective physiological roles, intra- and extracellular transport of androgens. The content of Rc-binding sites in caput epididymis was 18, in corpus 4 and in cauda 22 fmol/mg protein. J. Endocr. (1984) 103, 273–279