Garner S C, Peng T C, Toverud S U
Department of Pharmacology, School of Medicine, University of North Carolina, Chapel Hill 27599.
J Bone Miner Res. 1988 Jun;3(3):319-23. doi: 10.1002/jbmr.5650030311.
Moderate dietary restriction of calcium (0.1% Ca) was used to accentuate the changes in serum immunoreactive parathyroid hormone (iPTH) that had been reported earlier in lactating rats fed 0.4% Ca diet. In addition, the effects of this low-Ca diet on serum total and ionized Ca and iPTH during pregnancy, extended lactation, and weaning were examined. The positive correlation between serum total and ionized Ca was highly significant (r = 0.88, p less than 0.001, n = 120). Serum iPTH was significantly higher (36%) in pregnant rats on the day of parturition compared to nonmated controls, and there was a concomitant decrease in both total and ionized serum Ca. Within 1 day after parturition, however, serum Ca had risen to the control level. Serum iPTH remained significantly elevated during the first 2 weeks of lactation, and increased further during the third week of lactation to a level more than twice that of nonlactating controls. Serum Ca fell gradually during the second week of lactation. The high serum iPTH levels were maintained for another 2 weeks when lactation was extended with foster litters. Within 6 hr of removal of the suckling pups on day 16 of lactation, maternal serum ionized and total Ca had risen and serum iPTH had fallen; all three parameters were at levels similar to those of nonmated controls by 24-48 hr after weaning. The data suggest that serum ionized Ca is a major factor contributing to the hyperparathyroid state during lactation in rats fed a low-Ca diet.
采用适度限制钙饮食（0.1%钙）来强化血清免疫反应性甲状旁腺激素（iPTH）的变化，这种变化在先前报道的喂食0.4%钙饮食的泌乳大鼠中已出现。此外，还研究了这种低钙饮食对妊娠、延长哺乳期和断奶期间血清总钙、离子钙和iPTH的影响。血清总钙和离子钙之间的正相关性非常显著（r = 0.88，p < 0.001，n = 120）。与未交配的对照组相比，分娩当天怀孕大鼠的血清iPTH显著更高（36%），同时血清总钙和离子钙均下降。然而，分娩后1天内，血清钙已升至对照水平。在哺乳期的前2周，血清iPTH仍显著升高，并在哺乳期第3周进一步升高至非哺乳期对照组的两倍以上。哺乳期第2周血清钙逐渐下降。当用代乳仔鼠延长哺乳期时，高血清iPTH水平又维持了2周。在哺乳期第16天移除哺乳幼崽后的6小时内，母体血清离子钙和总钙升高，血清iPTH下降；断奶后24 - 48小时，所有这三个参数均处于与未交配对照组相似的水平。数据表明，血清离子钙是导致喂食低钙饮食的大鼠哺乳期甲状旁腺功能亢进状态的主要因素。
