Gravesen Eva, Mace Maria L, Hofman-Bang Jacob, Olgaard Klaus, Lewin Ewa
Nephrological Department P, Rigshospitalet, University of Copenhagen, 2100, Copenhagen, Denmark.
Calcif Tissue Int. 2014 Jul;95(1):46-53. doi: 10.1007/s00223-014-9861-8. Epub 2014 May 7.
The regulation of fibroblast growth factor 23 (FGF23) synthesis and secretion is still incompletely understood. FGF23 is an important regulator of renal phosphate excretion and has regulatory effects on the calciotropic hormones calcitriol and parathyroid hormone (PTH). Calcium (Ca) and phosphate homeostasis are closely interrelated, and it is therefore likely that Ca is involved in FGF23 regulation. It has recently been reported that dietary Ca influenced FGF23 levels, with high Ca increasing FGF23. The mechanism remains to be clarified. It remains unknown whether acute changes in plasma Ca influence FGF23 levels and whether a close relationship, similar that known for Ca and PTH, exists between Ca and FGF23. Thus, the aim of the present study was to examine whether acute hypercalcemia and hypocalcemia regulate FGF23 levels in the rat. Acute hypercalcemia was induced by an intravenous Ca infusion and hypocalcemia by infusion of ethylene glycol tetraacetic acid (EGTA) in normal and acutely parathyroidectomized rats. Intact plasma FGF23 and intact plasma PTH and plasma Ca(2+) and phosphate were measured. Acute hypercalcemia and hypocalcemia resulted as expected in adequate PTH secretory responses. Plasma FGF23 levels remained stable at all plasma Ca(2+) levels; acute parathyroidectomy did not affect FGF23 secretion. In conclusion, Ca is not a regulator of acute changes in FGF23 secretion.
成纤维细胞生长因子23（FGF23）合成与分泌的调节机制仍未完全明确。FGF23是肾脏磷酸盐排泄的重要调节因子，对钙调节激素骨化三醇和甲状旁腺激素（PTH）具有调节作用。钙（Ca）和磷酸盐的稳态密切相关，因此Ca可能参与FGF23的调节。最近有报道称，饮食中的Ca会影响FGF23水平，高Ca会使FGF23升高。其机制仍有待阐明。血浆Ca的急性变化是否会影响FGF23水平，以及Ca与FGF23之间是否存在类似于Ca与PTH之间已知的密切关系，目前尚不清楚。因此，本研究的目的是探讨急性高钙血症和低钙血症是否会调节大鼠体内的FGF23水平。在正常和急性甲状旁腺切除的大鼠中，通过静脉注射Ca诱导急性高钙血症，通过注射乙二醇四乙酸（EGTA）诱导低钙血症。检测完整血浆FGF23、完整血浆PTH以及血浆Ca(2+)和磷酸盐水平。急性高钙血症和低钙血症如预期引发了适当的PTH分泌反应。在所有血浆Ca(2+)水平下，血浆FGF23水平均保持稳定；急性甲状旁腺切除不影响FGF23的分泌。总之，Ca不是FGF23分泌急性变化的调节因子。
