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STUDY ON REGULATING MECHANISM FOR CALCIUM METABOLISM OF BONE CELLS THROUGH CALCITONIN RECEPTORS

降钙素受体调节骨细胞钙代谢机制的研究

基本信息

批准号：
10671870
负责人：
YASUOKA Tadashi
金额：
$ 2.05万
依托单位：
GIFU UNIVERSITY HOSPITAL
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

Laying White Leghorn hens, 18 to 20 months of age, were sacrificed at nine different times, and nonlaying hens were sacrificed at the corresponding hours. Additionally, 17β-estradiol, progesterone, 5α-dihydrotestosterone were intramuscularly administrated into nonlaying hens. These hens were sacrificed at 1, 2, and 4 hours after administration.Plasma membrane fractions were prepared from the periosteum of the calvaria and kidney. Samples were incubated at 4℃ for 1 h with various concentrations of chicken [^<125>I] calcitonin (CT) in the absence or presence of 1 μM unlabeled CT in a total volume of 300 μl. Free and bound ligands were separated by centrifugation, and radioactivity was determined by a γ-counter. Specific binding was obtained by subtracting the nonospecific binding from the total binding. The equilibrium dissociation constant (K_d) and the maximum binding capacity (B_<max>) were calculated by Scatchard's method.The K_d value of CT receptor of the calvaria and bone in the laying hens showed decreases at 3 h before and 2 hours after the oviposition. But, no changes in K_d values were observed in the nonlaying hens. The time of the decrease in K_d value accords with the time of increased secretion of the ovarian steroid hormones. In vivo administration of 17β-estradiol or progesterone induced a decrease in K_d value. The decrease in K_d value is suggested to be caused by either or both 17β-estradiol and progesterone. Decrease of B_<max> values in the calvarial and renal CT receptors were noted 3 h before oviposition in the laying hen, and the decrease preceded the changes in K_d values. Plasma CT level is elevated between 15 and 9 h before oviposition. The smaller B_<max> values CT receptors, therefore, may be consequence from the increase of the binding CT to the receptors in vivo by an increase of the affinity.

在9个不同时间处死18 ~ 20月龄的产蛋白色来航母鸡，在相应时间处死非产蛋母鸡。另外，对非产蛋母鸡肌肉注射17β-雌二醇、孕酮、5α-二氢睾酮。在给药后1、2和4小时处死这些母鸡，从颅骨和肾脏的骨膜制备质膜组分。在<125>不存在或存在1 μM未标记CT的情况下，将样品与不同浓度的鸡[^ I]降钙素（CT）在4℃下孵育1 h，总体积为300 μl。通过离心分离游离和结合配体，并通过γ计数器测定放射性。通过从总结合中减去非特异性结合来获得特异性结合。用Scatchard法计算了CT受体的平衡解离常数（Kd）和最大结合容量（B_<max>），结果表明，产蛋母鸡颅骨和骨骼CT受体的Kd值在产卵前3 h和产卵后2 h均呈下降趋势。而非产蛋鸡的K_d值无明显变化。K_d值下降的时间与卵巢类固醇激素分泌增加的时间相一致。在体内给予17β-雌二醇或孕酮可使K_d值降低。K_d值的降低可能是17β-雌二醇和孕酮之一或两者共同作用的结果。产<max>蛋母鸡在产卵前3 h，颅骨和肾脏CT感受器的B值下降，其下降先于Kd值的变化。产卵前15 ~ 9 h血浆CT水平升高。因此，CT受体的较小B值<max>可能是由于CT与受体在体内的结合通过亲和力的增加而增加的结果。