Paolucci M, Guerriero G, Ciarcia G
Facoltà di Scienze, Università degli Studi del Sannio, Benevento, Italy.
J Exp Zool. 1999 Dec 1;284(7):765-75. doi: 10.1002/(sici)1097-010x(19991201)284:7<765::aid-jez6>3.0.co;2-e.
Progesterone is a versatile hormone showing an ample variety of effects. One of the numerous functions attributed to progesterone is the modulation of vitellogenesis in oviparous vertebrates. As a prerequisite for the possible involvement of progesterone in vitellogenesis modulation, we investigated the presence of a progesterone receptor (PR) in the liver of the female green frog Rana esculenta. 3H-Progesterone (3H-P) binding activity was found in both cytosol and nuclear extract of the liver of Rana esculenta. The progesterone-binding moiety showed the typical characteristics of a true receptor, such as high affinity, low capacity, and specificity for progesterone. It also bound to DNA-cellulose and was eluted with a linear salt gradient at a concentration of 0.05 M of NaCl. The progesterone-binding moiety was down regulated by steroid hormones, in that ovariectomy resulted in a significant increase, in both cytosol and nuclear extract, of 3H-P binding activity with respect to intact females. On the contrary, 3H-P binding activity was almost undetectable after estradiol and/or progesterone treatment. The progesterone binding moiety of Rana esculenta was analyzed by Western blotting with the aid of a monoclonal antibody raised against the subunits A and B of the chicken PR. An immunoreactive band of about 67 kDa was observed in the liver of both intact and treated females. The 67 kDa band showed an increased intensity in ovariectomized animals, while it was faint following treatment with estradiol and/or progesterone. This is the first report on the presence of a progesterone receptor (PR) in the liver of an amphibian. PR of Rana esculenta is down regulated by estradiol and/or progesterone and shows peculiar immunological and biochemical characteristics, which make it rather different from the PR of other vertebrates.
孕酮是一种具有多种作用的多功能激素。孕酮的众多功能之一是调节卵生脊椎动物的卵黄生成。作为孕酮可能参与卵黄生成调节的前提条件，我们研究了雌性绿蛙（食用蛙）肝脏中孕酮受体（PR）的存在情况。在食用蛙肝脏的细胞质和核提取物中均发现了³H-孕酮（³H-P）结合活性。孕酮结合部分表现出真正受体的典型特征，如高亲和力、低容量以及对孕酮的特异性。它还能与DNA-纤维素结合，并在0.05 M NaCl浓度下通过线性盐梯度洗脱。孕酮结合部分受到类固醇激素的下调，即卵巢切除导致细胞质和核提取物中³H-P结合活性相对于完整雌性显著增加。相反，雌二醇和/或孕酮处理后³H-P结合活性几乎检测不到。借助针对鸡PR亚基A和B产生的单克隆抗体，通过蛋白质印迹法分析了食用蛙的孕酮结合部分。在完整和处理过的雌性蛙肝脏中均观察到一条约67 kDa的免疫反应条带。这条67 kDa的条带在卵巢切除的动物中强度增加，而在用雌二醇和/或孕酮处理后则很微弱。这是关于两栖动物肝脏中存在孕酮受体（PR）的首次报道。食用蛙的PR受到雌二醇和/或孕酮的下调，并表现出独特的免疫和生化特征，这使其与其他脊椎动物的PR有很大不同。
