Estrogen receptor in bovine skeletal muscle

In connection with investigations of the anabolic action of estrogens, we examined skeletal muscle of veal calves for estradiol receptors. The high speed supernatant of muscle homogenate was incubated with .5 nM 3H-estradiol and for the determination of nonspecific binding with .5 nM 3H-estradiol plus 13 nM estradiol at 0 C overnight. After treatment with charcoal two times, the supernatant was analyzed by agar gel electrophoresis. Specific binding was found in the typical position of cytosolic estradiol receptor. Ninety percent of 3H-estradiol binding was suppressed by estradiol-17 beta, zeranol, estrone or diethylstilbestrol, but was not affected by testosterone, dihydrotestosterone, trenbolone or progesterone. The specific binding activity varied between .3 and 2.0 fmol/mg protein and the dissociation constant of the receptor was Kd = 60 pM. After an enrichment up to 42 fmol/mg cytosolic protein using heparin sepharose, the receptor remained unchanged as determined by agar gel electrophoresis. Although uterine tissue generally contains 1,000 times more estradiol receptors, these results clearly demonstrate that skeletal muscle also contains estradiol receptors with identical properties. This indicates that one possible component of the anabolic action of estrogens may be the direct stimulation of the muscle via the estradiol receptor.