Lawrence W D, Osawa Y M, Davis P J, Blas S D
Endocrinology. 1986 Dec;119(6):2803-8. doi: 10.1210/endo-119-6-2803.
Physiological concentrations of L-T4 were found previously to stimulate Ca2+-ATPase activity in vitro in reticulocyte membranes from female rabbits and to inhibit this enzyme in reticulocyte membranes from males. In these previous studies, preincubation of intact cells or ghosts with testosterone (5 X 10(-11) M) converted female-source reticulocyte membranes to male-type responsiveness to thyroid hormone (inhibition of Ca2+-ATPase activity). Preincubation of reticulocyte membranes with 17 beta-estradiol (5 X 10(-11) M) converted male-source membranes to female-type responsiveness (stimulation by L-T4 of membrane Ca2+-ATPase activity). Using this sex steroid-sensitive thyroid hormone-dependent membrane enzyme system, we investigated the structure-activity relationships of analogs of sex steroids and unrelated steroids. 5 beta-Androstanes were active compared to testosterone in assays using female-source membranes, while 5 alpha-androstanes were less active. Within the 5 beta-androstanes, activity was dependent on at least one hydroxyl group at the C3- or C17-position. Nongonadal steroids tested were less active, establishing specificity of the sex steroid effect in assays using female-source membranes. Assayed in male-source membranes, estrone and 3-hydroxy-1,3,5-(10)7-estratraen-17-one (equilin) were active compared for estrogen effect with 17 beta-estradiol, while estriol was less active. The activities of hydrocortisone and aldosterone were 76% and 71%, respectively, in this system. These structure-activity relationships are distinct from those described for gonadal steroid-cytoplasmic binding proteins or nuclear interactions, and represent a novel sex steroid-thyroid hormone effect on activity of a membrane enzyme.
先前发现，生理浓度的L-T4在体外可刺激雌性兔网织红细胞膜中的Ca2+-ATP酶活性，而抑制雄性兔网织红细胞膜中的该酶活性。在这些先前的研究中，完整细胞或血影与睾酮（5×10−11M）预孵育，可使雌性来源的网织红细胞膜对甲状腺激素的反应转变为雄性类型（抑制Ca2+-ATP酶活性）。网织红细胞膜与17β-雌二醇（5×10−11M）预孵育，可使雄性来源的膜转变为雌性类型的反应（L-T4刺激膜Ca2+-ATP酶活性）。利用这种对性类固醇敏感的甲状腺激素依赖性膜酶系统，我们研究了性类固醇类似物和无关类固醇的构效关系。在使用雌性来源膜的测定中，与睾酮相比，5β-雄烷具有活性，而5α-雄烷活性较低。在5β-雄烷中，活性至少依赖于C3或C17位的一个羟基。所测试的非性腺类固醇活性较低，这在使用雌性来源膜的测定中确立了性类固醇效应的特异性。在雄性来源膜中进行测定时，与17β-雌二醇相比，雌酮和3-羟基-1,3,5-(10)7-雌三烯-17-酮（马萘雌酮）具有雌激素活性，而雌三醇活性较低。在该系统中，氢化可的松和醛固酮的活性分别为76%和71%。这些构效关系不同于性腺类固醇-细胞质结合蛋白或核相互作用所描述的关系，代表了性类固醇-甲状腺激素对膜酶活性的一种新效应。
