Fuentes Juan, Figueiredo Joana, Power Deborah M, Canário Adelino V 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. 2006 Nov;291(5):R1499-506. doi: 10.1152/ajpregu.00892.2005. Epub 2006 Jun 8.
Parathyroid hormone-related protein (PTHrP) is a factor associated with normal development and physiology of the nervous, cardiovascular, immune, reproductive, and musculoskeletal systems in higher vertebrates. It also stimulates whole body calcium uptake in sea bream (Sparus auratus) larvae with an estimated 60% coming from intestinal uptake in seawater. The present study investigated the role of PTHrP in the intestinal calcium transport in the sea bream in vitro. Unidirectional mucosal-to-serosal and serosal-to-mucosal 45Ca fluxes were measured in vitro in duodenum, hindgut, and rectum mounted in Ussing chambers. In symmetric conditions with the same saline, bathing apical and basolateral sides of the preparation addition of piscine PTHrP 1-34 (6 nM) to the serosal surface resulted in an increase in mucosal to serosal calcium fluxes in duodenum and hindgut and a reduction in serosal to mucosal in the rectum, indicating that different mechanisms are responsive to PTHrP along the intestine. In control asymmetric conditions, with serosal normal and mucosal bathed with a saline similar in composition to the intestinal fluid, there was a net increase in calcium uptake in all regions. The addition of 6 nM PTHrP 1-34 increased net calcium uptake two- to threefold in all regions. The stimulatory effect of PTHrP on net intestinal calcium absorption is consistent with a hypercalcemic role for the hormone. The results support the view that PTHrP, alone or in conjunction with recently identified PTH-like peptides, counteracts in vivo the hypocalcemic effects of stanniocalcin.
甲状旁腺激素相关蛋白（PTHrP）是一种与高等脊椎动物的神经、心血管、免疫、生殖和肌肉骨骼系统的正常发育及生理功能相关的因子。它还能刺激黑鲷（Sparus auratus）幼体对全身钙的摄取，估计其中60%来自海水中的肠道吸收。本研究在体外研究了PTHrP在黑鲷肠道钙转运中的作用。在安装于尤斯灌流室的十二指肠、后肠和直肠中，体外测量了单向的黏膜到浆膜以及浆膜到黏膜的45Ca通量。在相同盐溶液的对称条件下，将鱼的PTHrP 1-34（6 nM）添加到灌流液的浆膜表面，会导致十二指肠和后肠中黏膜到浆膜的钙通量增加，而直肠中浆膜到黏膜的钙通量减少，这表明沿着肠道不同机制对PTHrP有反应。在对照非对称条件下，浆膜侧为正常溶液，黏膜侧用与肠液成分相似的盐溶液灌流，所有区域的钙摄取都有净增加。添加6 nM的PTHrP 1-34使所有区域的净钙摄取增加了两到三倍。PTHrP对肠道净钙吸收的刺激作用与该激素的高钙血症作用一致。这些结果支持这样一种观点，即PTHrP单独或与最近鉴定出的类PTH肽一起，在体内抵消了鲷鱼降钙素的低钙血症作用。
