Some properties of androgen-binding activity in rat testis. |
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Authors: | B M Sanborn J S Elkington R K Tcholakian E Steinberger |
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Institution: | Program in Reproductive Biology and Endocrinology, The University of Texas Medical School at Houston, Houston, Texas 77025, U.S.A. |
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Abstract: | High-affinity (Ka approximately equal to 5 X 10(8) M-1 for testosterone) androgen-binding activity in rat testis was shown to have a rapid dissociation rate constant (t1/2 = 3 min, 0 degrees C, 30% glycerol buffer) using dextran-coated charcoal to separate bound from free hormone. Because of this fact, exchange of endogenous and labeled hormone was complete in the assay incubation time (16 h, 0 degrees C) and Scatchard plots of the high-affinity binding data were shown to measure total as contrasted to available sites. The binding was highly specific for androgens. Polyacrylamide gel electrophoresis separated high-affinity androgen-binding protein (Rf 0.54) from albumin (Rf 0.62). Binding site estimates under saturating conditions or by Scatchard analysis of electrophoresis data utilizing 3H]dihydrotestosterone agreed reasonably well with estimates made by the charcoal technique using 3H]testosterone. |
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Keywords: | androgen-binding protein polyacrylamide gel electrophoresis dextran-coated charcoal testosterone dihydrotestosterone testis dihydrotestosterone 5α-androstan-17β-ol-3-one 17α-hydroxypregnenolone 3β 17α-dihydroxy-5-pregnene-20-one |
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