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STUDY ON REGULATING MECHANISM FOR CLACIUM METABOLISM OF BONE CELLS VIA PARATHYROID HORMONE RECEPTORS

甲状旁腺激素受体调节骨细胞钙代谢机制的研究

基本信息

批准号：
08672297
负责人：
YASUOKA Tadashi
金额：
$ 1.41万
依托单位：
AFFILIATED HOSPITAL OF GIFU UNIVERSITY SCHOOL OF MEDICINE
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

Laying White Leghorn hens, 18 to 20 months of age, were killed at nine different times, and nonlaying hens were sacrificed at the corresponding hours. Additionally, 17beta-estradiol, progesterone, 5alpha-dihydrotestosterone were intramuscularly administrated into nonlaying hens. These hens were killed 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ﾟC for 1 h with various concentrations of chicken [^<125>I] PTHrP in the absence or presence of 1 muM unlabeledl PTHrP in a total volume of 300 mul. Free and bound ligands were separated by centrifugation, and radioactivity was determined by a gamma-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 determined by Scatchard's method.The K_d value of PTH receptor of the calvaria and bone in the laying hens showed decreases at 3 h before and the time of 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 17beta-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 17beta-estradiol and progesterone. Decrease of B_<max> values in the calvarial and renal PTH receptors were noted 6 h before oviposition in the laying hen, and the decrease preceded the changes in K_d values. Plasma PTH level is elevated between 15 and 9 h before oviposition. The smaller B_<max> values PTH receptors, therefore, may be consequence from the increase of the binding PTH 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，在相应时间处死未产蛋母鸡。此外，17 β-雌二醇，孕酮，5 α-双氢睾酮肌肉注射到非产蛋鸡。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中制备质膜组分。在<125>总体积为300穆尔的1 μ M未标记的PTHrP存在或不存在的情况下，将样品与不同浓度的鸡[μ I] PTHrP在4 ℃下孵育1小时。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法测定了PTH受体的平衡解离常数（Kd）和最大结合容量（B_<max>），结果表明，蛋鸡颅骨和骨骼PTH受体的Kd值在产卵前3 h和产卵后均呈下降趋势。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17 β-雌二醇或孕酮可使K_d值降低。K_d值的降低可能是17 β-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6 h，头盖骨和肾脏PTH受体的B值均下降，其下降先于Kd值的变化。血浆甲状旁腺素水平升高之间15和9小时产卵前。因此，较小的<max>PTH受体B值可能是由于体内PTH与受体结合的亲和力增加所致。