Changes in parathyroid hormone receptor binding affinity during egg laying: Implications for calcium homeostasis in chicken

✍ Scribed by Tadashi Yasuoka; Mitsuo Kawashima; Tetsuya Takahashi; Atsushi Iwata; Nobumitsu Oka; Katuhide Tanaka

• Book ID: 102875537
• Publisher: American Society for Bone and Mineral Research
• Year: 2010
• Tongue: English
• Weight: 680 KB
• Volume: 11
• Category: Article
• ISSN: 0884-0431
• DOI: 10.1002/jbmr.5650111212

✦ Synopsis

Parathyroid hormone (PTH) receptor bindings were examined in the membrane fraction of the calvaria and the kidney of the hen by the use of [ l 25I]PTH-related protein (PTHrP) binding assays. The binding specificity, reversibility, and saturation of the receptor were demonstrated. The equilibrium dissociation constant (K d ) and the maximum binding capacity (B m ax ) were obtained by Scatchard analyses. In both calvaria and kidney, K d and B m ax values decreased at 3 h before oviposition in egg-laying hens, but not in nonlaying hens. Administration of 17{J-estradiol or progesterone in vivocaused a decrease in the K d and B max values. Ionized calcium concentrations in the blood plasma showed a decrease at 13 h before oviposition. The results suggest that the PTH receptor binding in the calvaria and the kidney is affected by ovarian steroid honnones and may playa role in maintaining the calcium homeostasis in the egg-laying hen. (