Ruiz-Jarabo Ignacio, Gregório Silvia F, Fuentes Juan
Centre of Marine Sciences (CCMAR), Campus de Gambelas, Universidade do Algarve, 8005-139 Faro, Portugal.
Department of Physiology, Faculty of Biological Sciences, University Complutense Madrid, 28040 Madrid, Spain.
Biology (Basel). 2022 Jun 4;11(6):863. doi: 10.3390/biology11060863.
Calcium balance is of paramount importance for vertebrates. In fish, the endocrine modulators of calcium homeostasis include the stanniocalcin (STC), and some members of the parathyroid hormone (PTH) family, such as the PTH-related protein (PTHrP), acting as antagonists. STC is ubiquitously expressed in higher vertebrates. In turn, bony fish exhibit specific STC-producing glands named the corpuscles of Stannius (CS). Previous studies pointed to a calcium-sensing receptor (CaSR) involvement in the secretion of STC, but little is known of the involvement of other putative regulators. The CS provides a unique model to deepen the study of STC secretion. We developed an ex vivo assay to culture CS of fish and a competitive ELISA method to measure STC concentrations. As expected, STC released from the CS responds to CaSR stimulation by calcium, calcimimetics, and calcilytic drugs. Moreover, we uncover the presence (by PCR) of two PTHrP receptors in the CS, e.g., PTH1R and PTH3R. Thus, ex vivo incubations revealed a dose-response inhibition of STC secretion in response to PTHrP at basal Ca concentrations. This inhibition is achieved through specific and reversible second messenger pathways (transmembrane adenylyl cyclases and phospholipase C), as the use of specific inhibitors highlights. Together, these results provide evidence for endocrine modulation between two antagonist hormones, STC and PTHrP.
钙平衡对脊椎动物至关重要。在鱼类中，钙稳态的内分泌调节因子包括鲽鱼降钙素（STC）以及甲状旁腺激素（PTH）家族的一些成员，如甲状旁腺激素相关蛋白（PTHrP），它们起拮抗剂作用。STC在高等脊椎动物中普遍表达。相反，硬骨鱼具有名为斯坦尼小体（CS）的特定分泌STC的腺体。先前的研究指出钙敏感受体（CaSR）参与STC的分泌，但对其他假定调节因子的参与了解甚少。CS为深入研究STC分泌提供了一个独特的模型。我们开发了一种体外试验来培养鱼类的CS，并建立了一种竞争性酶联免疫吸附测定法来测量STC浓度。正如预期的那样，从CS释放的STC对钙、钙敏感受体激动剂和钙敏感受体拮抗剂药物引起的CaSR刺激有反应。此外，我们通过聚合酶链反应（PCR）发现CS中存在两种PTHrP受体，即PTH1R和PTH3R。因此，体外孵育显示在基础钙浓度下，PTHrP对STC分泌有剂量反应抑制作用。这种抑制是通过特定且可逆的第二信使途径（跨膜腺苷酸环化酶和磷脂酶C）实现的，因为使用特定抑制剂突出了这一点。总之，这些结果为两种拮抗激素STC和PTHrP之间的内分泌调节提供了证据。
