Costlow M E, Buschow R A, McGuire W L
Cancer Res. 1976 Sep;36(9 pt.1):3324-9.
Prolactin reverses the inhibitory effects of pharmacological doses of androgen on 7,12-dimethylbenz(a)anthracene-induced mammary tumor growth (Quadri, S.K., Kledzik, G.S., and Meites, J.J. Natl. Cancer Inst., 52: 875-878,1974). To determine whether this effect is due to an alteration in the ability of the tumor cell to bind prolactin, we have quantitated prolactin receptors in androgen-responsive and nonresponsive tumors. Prolactin receptors were measured with 125I-labeled ovine prolactin in a subcellular fraction which reproducibly contained 60 to 80% of the total receptor present in tumor homogenates. Prolactin binding was reversible, reached a steady state in 9 hr, and was completed by excess unlabeled prolactin. Prolactin bound to its receptor with a Kd of approximately 1 X 10(-10) M. Growing tumors were biopsied, and rats bearing regrown tumors were given injections of 4 mg testosterone propionate twice a week. Prolactin receptors were reduced in most of the tumors, which regressed after testosterone treatment by an average of 63% compared to the pretreatment biopsy specimens. Nonresponsive tumors and vehicle-injected controls showed no signifcant alterations in receptor content. This reduction of prolactin receptors is probably insufficient to account for androgen-induced mammary tumor regression.
催乳素可逆转药理剂量雄激素对7,12 - 二甲基苯并(a)蒽诱导的乳腺肿瘤生长的抑制作用（Quadri, S.K., Kledzik, G.S., and Meites, J.《美国国家癌症研究所杂志》，52: 875 - 878,1974）。为了确定这种作用是否是由于肿瘤细胞结合催乳素的能力发生改变，我们对雄激素反应性和无反应性肿瘤中的催乳素受体进行了定量。用125I标记的绵羊催乳素在一个亚细胞组分中测量催乳素受体，该组分可重复地包含肿瘤匀浆中总受体的60%至80%。催乳素结合是可逆的，在9小时内达到稳态，并可被过量的未标记催乳素完全竞争。催乳素与其受体结合的解离常数约为1×10(-10)M。对生长中的肿瘤进行活检，对携带再生肿瘤的大鼠每周两次注射4毫克丙酸睾酮。大多数肿瘤中的催乳素受体减少，与预处理活检标本相比，睾酮治疗后肿瘤平均消退63%。无反应性肿瘤和注射赋形剂的对照组受体含量无显著变化。催乳素受体的这种减少可能不足以解释雄激素诱导的乳腺肿瘤消退。
