Endocrinology, Vol 130, 1909-1915, Copyright © 1992 by Endocrine Society

ARTICLES

Development and validation of a radioimmunoassay for mouse osteocalcin: paradoxical response in the Hyp mouse

CM Gundberg, ME Clough and TO Carpenter
Department of Orthopedics and Rehabilitation, Yale University School of Medicine, New Haven, Connecticut 06510.

The hypophosphatemic (Hyp) mouse is a model for human familial hypophosphatemic rickets. To test the hypothesis that there is an osteoblastic defect in these animals, serum osteocalcin levels were measured in Hyp mice and their normal littermates. Furthermore, the effects of phosphorus deprivation, phosphorus loading, and 1,25- dihydroxyvitamin D3 administration on serum osteocalcin levels were examined. Osteocalcin was purified from mouse hindlimbs, and a polyclonal antibody to this material was produced in a goat. The antibody recognized native and decarboxylated mouse osteocalcin, but could not recognize osteocalcin from several other species. A RIA was developed which had a minimal detection limit of 0.4 nmol/liter (2.2 micrograms/liter) and half-maximal displacement at 2.7-3.3 nmol/liter (14.8-18.2 micrograms/liter). The intraassay coefficient of variation was 6.4%, while the interassay coefficient of variation was 12%. Dilutions of mouse serum samples varied by less than 15%. Analytical recovery was typically greater than 90%. Serum osteocalcin concentrations in Hyp and normal mice were shown to decrease with age. However, circulating osteocalcin levels in Hyp mice were higher than those in their normal littermates regardless of the age of the animal (P less than 0.001). One week of a high phosphorus diet resulted in an increase in serum phosphate in normal and Hyp mice, but serum osteocalcin concentrations were unaffected. On the other hand, dietary phosphorus deprivation for 4 weeks resulted in comparable hypophosphatemia in both Hyp and normal mice, and serum osteocalcin increased in both groups of animals. Intraperitoneal injection of 30 ng/day 1,25-dihydroxyvitamin D3 for 7 days resulted in a 215 +/- 33% increase in serum osteocalcin in normal animals, while the same regimen produced a 250 +/- 29% decrease in the Hyp mouse. Our results are consistent with the hypothesis that abnormal osteoblastic activity is present in Hyp mice. Furthermore, hypophosphatemia may be a general regulator of osteocalcin synthesis or secretion in the mouse.

This article has been cited by other articles:

				T. Kawano, N. Troiano, D. J. Adams, J. Jun Wu, B.-h. Sun, and K. Insogna The Anabolic Response to Parathyroid Hormone Is Augmented in Rac2 Knockout Mice Endocrinology, August 1, 2008; 149(8): 4009 - 4015. [Abstract] [Full Text] [PDF]

				E. Knopp, N. Troiano, M. Bouxsein, B.-h. Sun, K. Lostritto, C. Gundberg, J. Dziura, and K. Insogna The Effect of Aging on the Skeletal Response to Intermittent Treatment with Parathyroid Hormone Endocrinology, April 1, 2005; 146(4): 1983 - 1990. [Abstract] [Full Text] [PDF]

				T. Onishi, T. Ogawa, T. Hayashibara, T. Hoshino, R. Okawa, and T. Ooshima Hyper-expression of Osteocalcin mRNA in Odontoblasts of Hyp Mice J. Dent. Res., January 1, 2005; 84(1): 84 - 88. [Abstract] [Full Text] [PDF]

				M. C. Horowitz, Y. Xi, D. L. Pflugh, D. G. T. Hesslein, D. G. Schatz, J. A. Lorenzo, and A. L. M. Bothwell Pax5-Deficient Mice Exhibit Early Onset Osteopenia with Increased Osteoclast Progenitors J. Immunol., December 1, 2004; 173(11): 6583 - 6591. [Abstract] [Full Text] [PDF]

				J. N. VanHouten and J. J. Wysolmerski Low Estrogen and High Parathyroid Hormone-Related Peptide Levels Contribute to Accelerated Bone Resorption and Bone Loss in Lactating Mice Endocrinology, December 1, 2003; 144(12): 5521 - 5529. [Abstract] [Full Text] [PDF]

				S. Liu, R. Guo, Q. Tu, and L. D. Quarles Overexpression of Phex in Osteoblasts Fails to Rescue the Hyp Mouse Phenotype J. Biol. Chem., January 25, 2002; 277(5): 3686 - 3697. [Abstract] [Full Text] [PDF]

				E. M. GARDINER, P. A. BALDOCK, G. P. THOMAS, N. A. SIMS, N. K. HENDERSON, B. HOLLIS, C. P. WHITE, K. L. SUNN, N. A. MORRISON, W. R. WALSH, et al. Increased formation and decreased resorption of bone in mice with elevated vitamin D receptor in mature cells of the osteoblastic lineage FASEB J, October 1, 2000; 14(13): 1908 - 1916. [Abstract] [Full Text]

				Z. S. Xiao, M. Crenshaw, R. Guo, T. Nesbitt, M. K. Drezner, and L. D. Quarles Intrinsic mineralization defect in Hyp mouse osteoblasts Am J Physiol Endocrinol Metab, October 1, 1998; 275(4): E700 - E708. [Abstract] [Full Text] [PDF]

				A. F. Ruchon, M. Marcinkiewicz, G. Siegfried, H. S. Tenenhouse, L. DesGroseillers, P. Crine, and G. Boileau Pex mRNA Is Localized in Developing Mouse Osteoblasts and Odontoblasts J. Histochem. Cytochem., April 1, 1998; 46(4): 459 - 468. [Abstract] [Full Text]

				T. O. Carpenter, K. C. Moltz, B. Ellis, M. Andreoli, T. L. McCarthy, M. Centrella, D. Bryan, and C. M. Gundberg Osteocalcin Production in Primary Osteoblast Cultures Derived from Normal and Hyp Mice Endocrinology, January 1, 1998; 139(1): 35 - 43. [Abstract] [Full Text] [PDF]

				N. A. Sims, C. P. White, K. L. Sunn, G. P. Thomas, M. L. Drummond, N. A. Morrison, J. A. Eisman, and E. M. Gardiner Human and Murine Osteocalcin Gene Expression: Conserved Tissue Restricted Expression and Divergent Responses to 1,25-Dihydroxyvitamin D3 in Vivo Mol. Endocrinol., October 1, 1997; 11(11): 1695 - 1708. [Abstract] [Full Text]

				B. Frenkel, C. Capparelli, M. van Auken, D. B. , J. Bryan, J. L. Stein, G. S. Stein, and J. B. Lian Activity of the Osteocalcin Promoter in Skeletal Sites of Transgenic Mice and during Osteoblast Differentiation in Bone Marrow-Derived Stromal Cell Cultures: Effects of Age and Sex Endocrinology, May 1, 1997; 138(5): 2109 - 2116. [Abstract] [Full Text] [PDF]

				J. B. Lian, V. Shalhoub, F. Aslam, B. Frenkel, J. Green, M. Hamrah, G. S. Stein, and J. L. Stein Species-Specific Glucocorticoid and 1,25-Dihydroxyvitamin D Responsiveness in Mouse MC3T3-E1 Osteoblasts: Dexamethasone Inhibits Osteoblast Differentiation and Vitamin D Down-Regulates Osteocalcin Gene Expression Endocrinology, May 1, 1997; 138(5): 2117 - 2127. [Abstract] [Full Text] [PDF]