Glucocorticoid binding in the hen oviduct |
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Authors: | Virinder K. Moudgil Shaun P. Healy Tamara L. Shaffer James F. Szocik |
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Affiliation: | Department of Biological Sciences, Oakland University, Rochester, MI 48063, U.S.A. |
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Abstract: | [3H]Triamcinolone acetonide (15nm) was incubated with cytosol (150000g fraction) prepared from oviducts of egg-laying hens. The extent of steroid binding, as determined by charcoal assays, was greatest between 2–4h at 4°C. A similar time curve was obtained when cytosol preparations were first fractionated with (NH4)2SO4 before labelling. The addition of 10mm-Na2MoO4 or 10mm-ATP during the incubation of hen oviduct cytosol with [3H]triamcinolone acetonide lowered the extent of steroid binding. The presence of glycerol (20%), however, increased the extent of [3H]triamcinolone acetonide binding in cytosol fractions from chick (330%) and hen (160%) oviducts. The [3H]triamcinolone acetonide–receptor complex was stable for over 4h at 4°C, but dissociated rapidly at 37°C, exhibiting a half-life of about 10min. The presence of 10mm-Na2MoO4 and 10mm-ATP or both had a small protective effect on the dissociation of [3H]triamcinolone acetonide–receptor complex. The receptor from hen oviduct showed significant affinity for unlabelled triamcinolone acetonide, cortisol, compound R5020 and dihydrotestosterone and, to a lesser extent, for oestradiol, oestrone and progesterone. Diethylstilboestrol treatment of immature chicks appeared to induce a more specific binder, which showed affinity for unlabelled triamcinolone acetonide, cortisol and compound R5020 only. Scatchard analysis of [3H]triamcinolone acetonide binding in hen oviduct cytosol revealed a Kd value of 6.4nm. The steroid–receptor complex sedimented as a 7–8S and a 4S entity on low-salt (0.01m-KCl)- and high-salt (0.3m-KCl)-containing sucrose gradients respectively. The cytosol [3H]triamcinolone acetonide–receptor complex showed no affinity for ATP–Sepharose or DNA–cellulose, but acquired this ability on heat activation (23°C, 40min). The data indicate the avian oviduct possesses a high-affinity binding molecule that fulfils the criteria of a glucocorticoid receptor. |
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