Binding of Steroid Hormones by the 105,000 x g Supernatant Fraction from Homogenates of Rat Skin and Variations during the Hair Cycle

Binding for testosterone, 5α-dihydrotestosterone, estradiol-17β, and progesterone by the 105,000 x g supernatant fraction of homogenates of rat skin was demonstrated by equilibrium dialysis. The binding ability was pH-dependent (maximum binding for 5α-dihydrotestosterone at pH 7.5) and was destroyed after heating at 60° for 5 min. The content of soluble proteins in rat skin was found to increase and decrease cyclically with the growing (anagen), transition (catagen), and resting (telogen) phases of the hair cycle, and in anagen the content was about twice that in telogen. Binding for testosterone, 5α-dihydrotestosterone, and estradiol-17β also fluctuated cyclically. Maximum binding for testosterone was in catagen, and for 5α-dihydrotestosterone and estradiol-17β in telogen. Minimum binding for both androgens was in mid-anagen, whereas for estradiol-17β was in late telogen or early anagen. Binding for progesterone was demonstrable but did not show remarkable variation. Gel filtration through Sephadex G-200 estimated the molecular weight of the binding protein for 5α-dihydrotestosterone at about 9 x 104, while that for estradiol-17β was about 5 x 104.