Schultz V L, Boass A, Garner S C, Toverud S U
Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill, USA.
J Bone Miner Res. 1997 Jun;12(6):903-8. doi: 10.1359/jbmr.1997.12.6.903.
We have previously shown that the serum parathyroid hormone (PTH) concentration in lactating (L) rats is not suppressed by high serum Ca2+ to the same extent as in nonmated (NM) rats. To investigate further Ca2+ regulation of PTH secretion, parathyroid cells from NM rats and rats in late pregnancy and at peak lactation were dispersed and incubated for 2 h in medium containing 0.52-2.05 mM Ca2+. Medium PTH was assayed with a homologous immunoradiometric assay (IRMA). At the two highest Ca2+ levels (1.81 and 2.05 mM), medium PTH was significantly higher (p = 0.031) for cells from L rats than for cells from NM rats. In contrast, significantly less (p < 0.001) PTH was secreted for the L group versus the NM group at medium Ca2+ values of 1.27 and 1.46 mM. Estimated set points for L and NM groups were 1.17 mM and 1.35 mM, respectively, corresponding closely to the prevailing serum Ca2+ for these two groups. Consistent with the present in vitro data, high serum PTH (> 40 pg/ml) in L rats occurred only at serum Ca2+ values below 1.27 mM. Elevated serum PTH at lower serum Ca2+ levels was also seen in pregnant rats. Dispersed parathyroid cells from 20- to 21-day pregnant rats secreted significantly more PTH (p = 0.028) than cells from NM rats at all Ca2+ levels tested (1.1-1.6 mM). In conclusion, the relationship between extracellular Ca2+ and PTH secretion is altered in rats during late pregnancy and at peak lactation, perhaps as part of the adaptation to the demands for calcium for pre- and postnatal growth.
我们之前已经表明，与未交配（NM）的大鼠相比，泌乳（L）大鼠的血清甲状旁腺激素（PTH）浓度不会被高血清Ca2+抑制到相同程度。为了进一步研究Ca2+对PTH分泌的调节，将来自NM大鼠、妊娠晚期大鼠和泌乳高峰期大鼠的甲状旁腺细胞分散，并在含有0.52 - 2.05 mM Ca2+的培养基中孵育2小时。用同源免疫放射分析（IRMA）测定培养基中的PTH。在两个最高Ca2+水平（1.81和2.05 mM）下，L组大鼠细胞的培养基PTH显著高于（p = 0.031）NM组大鼠细胞。相反，在培养基Ca2+值为1.27和1.46 mM时，L组分泌的PTH明显少于（p < 0.001）NM组。L组和NM组的估计设定点分别为1.17 mM和1.35 mM，与这两组的当前血清Ca2+密切对应。与目前的体外数据一致，L组大鼠仅在血清Ca2+值低于1.27 mM时出现高血清PTH（> 40 pg/ml）。在妊娠大鼠中也观察到较低血清Ca2+水平时血清PTH升高。在所有测试的Ca2+水平（1.1 - 1.6 mM）下，来自妊娠20 - 21天大鼠的分散甲状旁腺细胞分泌的PTH明显多于（p = 0.028）NM组大鼠细胞。总之，妊娠晚期和泌乳高峰期大鼠细胞外Ca2+与PTH分泌之间的关系发生了改变，这可能是对产前和产后生长对钙需求的适应的一部分。
