Fuentes Juan, Guerreiro Pedro M, Modesto Teresa, Rotllant Josep, Canario Adelino V M, Power Deborah M
Centro de Ciências do Mar, CIMAR-Laboratório Associado, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal.
Am J Physiol Regul Integr Comp Physiol. 2007 Aug;293(2):R956-60. doi: 10.1152/ajpregu.00111.2007. Epub 2007 May 30.
Estradiol (E(2)) increases circulating calcium and phosphate levels in fish, thus acting as a hypercalcemic and hyperphosphatemic factor during periods of high calcium requirements, such as during vitellogenesis. Since parathyroid hormone (PTH)-related protein (PTHrP) has been shown to be calciotropic in fish, we hypothesized that the two hormones could be mediating the same process. Sea bream (Sparus auratus) juveniles receiving a single intraperitoneal injection of piscine PTHrP(1-34) showed an elevation in calcium plasma levels within 24 h. In contrast, injections of the PTH/PTHrP receptor antagonist PTHrP(7-34) decreased circulating levels of calcium in the same period. Intraperitoneal implants of estradiol-17beta (E(2); 10 microg/g) evoked significant increases of circulating plasma levels of calcium and phosphorus and a sustained increases of circulating plasma levels of PTHrP. However, a combined treatment of E(2) and PTHrP(7-34) evoked a markedly lower calcium response compared with E(2) alone. We conclude that PTHrP or a related peptide that binds the PTH/PTHrP receptor mediates, at least in part, the hypercalcemic effect of E(2) in calcium and phosphate balance in fish.
雌二醇（E₂）可提高鱼类的循环钙和磷水平，因此在钙需求较高的时期，如卵黄发生期，它作为一种高钙血症和高磷血症因子发挥作用。由于甲状旁腺激素（PTH）相关蛋白（PTHrP）已被证明在鱼类中具有钙调节作用，我们推测这两种激素可能介导相同的过程。接受单次腹腔注射鱼PTHrP(1 - 34)的黑鲷幼鱼在24小时内血浆钙水平升高。相反，注射PTH/PTHrP受体拮抗剂PTHrP(7 - 34)在同一时期降低了循环钙水平。腹腔植入17β - 雌二醇（E₂；10微克/克）引起循环血浆钙和磷水平显著升高以及循环血浆PTHrP水平持续升高。然而，与单独使用E₂相比，E₂和PTHrP(7 - 34)联合治疗引起的钙反应明显较低。我们得出结论，PTHrP或与PTH/PTHrP受体结合的相关肽至少部分介导了E₂在鱼类钙和磷平衡中的高钙血症作用。
