Long-term castration decreases the androgen but not the estrogen nuclear pituitary receptors in the ram.
The effect of castration on pituitary androgen and estrogen nuclear receptors was examined in eleven 3-year-old 'Préalpes du Sud' rams which were either intact (N = 5) or surgically castrated (N = 6) 11 months before. To avoid a receptor loss, pituitaries were frozen less than 1 min after slaughter. Specific androgen and estrogen bindings were measured upon extracts from purified nuclei. Neither the concentration of estrogen receptors (30.5 +/- 3.0 vs 28.1 +/- 3.0 fmol/mg protein) nor the affinity constant (ka = 1.21 X 10(9) mol-1 in both groups) differed between intact and castrated rams. Conversely, androgen receptor concentrations differed markedly between groups and were found significantly higher in intact rams (11.3 +/- 1.1 fmol/mg protein) than in castrated rams where nuclear receptors were undetectable in 5 out of 6 animals. This result keeps open the possibility that the decrease of LH sensitivity to testosterone negative feedback observed after long-term castration, could be related to the quasi absence of nuclear receptors, at least at the pituitary level.
Thieulant
M L
ML
Laboratory of General Biochemistry, U.A. CNRS 256, Campus de Beaulieu, Rennes, France.
Pelletier
J
J
D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D013196:Dihydrotestosterone / Q000378:metabolism; D004958:Estradiol / Q000378:metabolism; D008297:Male; D009919:Orchiectomy; D010902:Pituitary Gland / Q000378:metabolism*; D011944:Receptors, Androgen / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000378:metabolism*; D012756:Sheep; D013997:Time Factors
D011944:Receptors, Androgen; D011960:Receptors, Estrogen; D013196:Dihydrotestosterone; D004958:Estradiol