Frairia R, Fortunati N, Berta L, Fazzari A, Fissore F, Gaidano G
Dipartimento di Fisiopatologia Clinica, Università di Torino, Italy.
J Steroid Biochem Mol Biol. 1991;40(4-6):805-12. doi: 10.1016/0960-0760(91)90306-p.
Since the discovery of a specific membrane binding site for sex steroid binding protein (SBP) in human decidual endometrium and in hyperplastic prostate numerous speculations have been raised on the existence of an additional non-receptor-mediated system for steroid hormone action. In the present work SBP cell membrane binding was investigated in human estrogen target tissues other than those previously studied either in the absence of steroids or in the presence of varying amounts (10(-10)-10(-6) M) of estradiol, testosterone and dihydrotestosterone, respectively. Plasma membranes obtained by differential centrifugation from homogenized samples of pre-menopausal endometrium, endometrium adenocarcinoma, normal liver and post-menopausal breast showed a specific binding of highly purified [125I]SBP: a major displacement of labeled SBP was elicited by radioinert SBP, while no significant displacement occurred when other human plasma proteins were used as cold competitors (molar excess ranging 500-10,000-fold). A specific, time-dependent binding of [125I]SBP was also observed in MCF-7 and in Hep-G2 cell lines. The different patterns of specific binding, observed in membranes from different tissues when SBP was liganded with different sex steroid molecules, leads us to consider the tissue individuality of the receptor as a further entity in the membrane recognition system for SBP.
自从在人蜕膜子宫内膜和增生性前列腺中发现性类固醇结合蛋白（SBP）的特异性膜结合位点以来，人们对类固醇激素作用存在一种额外的非受体介导系统提出了众多猜测。在本研究中，我们分别在无类固醇或存在不同量（10⁻¹⁰ - 10⁻⁶ M）雌二醇、睾酮和双氢睾酮的情况下，对除先前研究过的组织之外的人雌激素靶组织中的SBP细胞膜结合进行了研究。通过差速离心从绝经前子宫内膜、子宫内膜腺癌、正常肝脏和绝经后乳腺的匀浆样品中获得的质膜显示出高度纯化的[¹²⁵I]SBP的特异性结合：放射性惰性SBP引起标记的SBP的主要位移，而当使用其他人血浆蛋白作为冷竞争剂（摩尔过量范围为500 - 10,000倍）时，未发生明显位移。在MCF - 7和Hep - G2细胞系中也观察到[¹²⁵I]SBP的特异性、时间依赖性结合。当SBP与不同的性类固醇分子结合时，在来自不同组织的膜中观察到的特异性结合的不同模式，使我们将受体的组织个体性视为SBP膜识别系统中的另一个实体。
