Paul Sudipta, Mukherjee Dola, Pramanick Kousik, Kundu Sourav, Bhattacharyya S P, De Priyanka, Mukherjee Dilip
Endocrinology Laboratory, Department of Zoology, University of Kalyani, Kalyani 741235, West Bengal, India.
J Endocrinol. 2008 Feb;196(2):413-24. doi: 10.1677/JOE-07-0188.
The effects of salmon calcitonin (sCT) on the secretion of 17beta-estradiol (E(2)) were examined in female common carp, Cyprinus carpio. Vitellogenic stage fish adapted to high-Ca water were i.p. injected with vehicle, sCT, human chorionic gonadotropin (hCG), or hCG plus sCT. To determine whether ovarian follicles are equipped with CT receptors, a CT binding assay was conducted. In the in vitro experiments, vitellogenic follicles were incubated with stimulators and inhibitors. Administration of sCT increased the basal and hCG-stimulated E(2) release in vivo and in vitro. Binding characteristics of [(125)I]sCT to plasma membrane preparation of carp ovarian follicles showed saturability with high-affinity (K(d)=48.48 pmol/l and B(max)=1.2 pmol/mg protein). To clarify the mechanism of E(2) production by sCT, in vitro effect of sCT and hCG on aromatase activity (conversion of testosterone to E(2)) and cytochrome P450 aromatase (P450arom) gene expression in carp ovarian follicles were investigated. Salmon CT-stimulated both aromatase activity and P450arom gene expression in ovarian follicles of carp. sCT-stimulated E(2) release by the ovarian follicles in vitro was augmented in the presence of dibutyryl cAMP. Inhibitor of protein kinase A (PKA), SQ 22536 inhibited sCT-stimulated steroid production in a dose-dependent manner. Specific inhibitor of protein kinase C (PKC), NPC-15437 dihydrochloride had no inhibitory effects on sCT-induced E(2) release. The present study indicates that sCT binds specifically to carp ovary and stimulates E(2) production by increasing the activity of cytochrome P450 aromatase and P450arom gene expression. The results further suggest that stimulatory action of sCT on E(2) production is mediated through cAMP pathway.
在雌性鲤鱼（Cyprinus carpio）中研究了鲑鱼降钙素（sCT）对17β-雌二醇（E₂）分泌的影响。将适应高钙水的卵黄生成期鱼类腹腔注射溶剂、sCT、人绒毛膜促性腺激素（hCG）或hCG加sCT。为了确定卵巢卵泡是否配备有降钙素受体，进行了降钙素结合试验。在体外实验中，将卵黄生成期卵泡与刺激剂和抑制剂一起孵育。sCT给药增加了体内和体外基础及hCG刺激的E₂释放。[(¹²⁵)I]sCT与鲤鱼卵巢卵泡质膜制剂的结合特性显示具有高亲和力的饱和性（Kd = 48.48 pmol/l，Bmax = 1.2 pmol/mg蛋白质）。为了阐明sCT产生E₂的机制，研究了sCT和hCG对鲤鱼卵巢卵泡中芳香化酶活性（睾酮转化为E₂）和细胞色素P450芳香化酶（P450arom）基因表达的体外作用。鲑鱼降钙素刺激了鲤鱼卵巢卵泡中的芳香化酶活性和P450arom基因表达。在二丁酰环磷腺苷（dibutyryl cAMP）存在下，sCT刺激的体外卵巢卵泡E₂释放增加。蛋白激酶A（PKA）抑制剂SQ 22536以剂量依赖性方式抑制sCT刺激的类固醇生成。蛋白激酶C（PKC）特异性抑制剂盐酸NPC - 15437对sCT诱导的E₂释放没有抑制作用。本研究表明，sCT特异性结合鲤鱼卵巢，并通过增加细胞色素P450芳香化酶的活性和P450arom基因表达来刺激E₂产生。结果进一步表明，sCT对E₂产生的刺激作用是通过环磷腺苷途径介导的。
