Dopplet S H, Talmage R V
Clin Orthop Relat Res. 1976 Jul-Aug(118):242-50.
Changes in plasma calcium and 45Ca concentrations were followed after injection of calcitonin or a combination of calcitonin (CT) and parathyroid hormone (PTH) into thyroparathyroidectomized rats maintained on thyroxine. Comparison was made between rats injected with the hormone(s) after a recent feeding and after an overnight fast. Also cor (18 hr 45Ca) before, and more than 6 days (greater than 6 day 45Ca) prior to hormone administration. The following results were obtained: The action of CT predominated over that of PTH for the first few hours after injection. However, the effects of PTH were eventually manifested even when additional CT was administered. In the "greater than 6 day" 45Ca groups, PTH normally produced an increase in plasma 45Ca specific activity. However, in fasted rats, plasms 45Ca fell with total calcium with no change in specific activity following CT injection. In fed rats CT injection was followed by a decrease in plasma 45Ca specific activity. When both hormones were administered plasma 45Ca specific activity changes mimicked those produced by CT alone even after PTH plasma effects were manifested. In the "18 hr" 45Ca groups, CT produced first a drop in plasma 45Ca, followed by a reduction in the rate of its removal from plasma. It is concluded that the data can best be explained by the postulate that plasma calcium concentrations are maintained by the control of fluxes between bone fluid in the osteocyte-lining cell bone unit and the extracellular fluid. PTH increases the efflux from this bone fluid compartment while CT restricuts the source of calcium and, therefore, the efflux. Plasma 45Ca changes are due to a combination of changes in flux rates and mixing processes between the extracellular fluid compartment and the bone fluid compartment.
给维持甲状腺素水平的甲状旁腺切除大鼠注射降钙素或降钙素（CT）与甲状旁腺激素（PTH）的组合后，跟踪血浆钙和45Ca浓度的变化。对近期进食后和禁食过夜后注射激素的大鼠进行了比较。还比较了激素给药前的cor（18小时45Ca）和给药前超过6天（大于6天45Ca）的情况。获得了以下结果：注射后的最初几个小时内，CT的作用比PTH的作用占主导。然而，即使给予额外的CT，PTH的作用最终还是会显现出来。在“大于6天”的45Ca组中，PTH通常会使血浆45Ca比活性增加。然而，在禁食大鼠中，注射CT后血浆45Ca随总钙下降，比活性无变化。在喂食大鼠中，注射CT后血浆45Ca比活性下降。当同时给予两种激素时，即使PTH的血浆作用显现后，血浆45Ca比活性的变化也模仿了单独给予CT时产生的变化。在“18小时”的45Ca组中，CT首先使血浆45Ca下降，随后其从血浆中的清除率降低。结论是，这些数据最好用以下假设来解释：血浆钙浓度通过控制骨细胞-衬里细胞骨单位中的骨液与细胞外液之间的通量来维持。PTH增加了从该骨液隔室的流出，而CT限制了钙的来源，从而限制了流出。血浆45Ca的变化是由于通量率的变化以及细胞外液隔室与骨液隔室之间的混合过程的综合作用。
