Determination of bioactive rat parathyroid hormone (PTH) concentrations in vivo and in vitro by a 2-site homologous immunoradiometric assay

A new homologous 2-site assay for rat parathyroid hormone (IRMA), developed by Immutopics, Inc., has been evaluated and compared with a bone cell cAMP bioassay. Circulating PTH for adult rats assayed with this IRMA are in the range 10–15 pg/ml, and of the same order of magnitude as published values...

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Veröffentlicht in:Bone and mineral 1994-11, Vol.27 (2), p.121-132
Hauptverfasser: Schultz, Vijitha L., Garner, Sanford C., Lavigne, Jeffrey R., Toverud, Svein U.
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Sprache:eng
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Zusammenfassung:A new homologous 2-site assay for rat parathyroid hormone (IRMA), developed by Immutopics, Inc., has been evaluated and compared with a bone cell cAMP bioassay. Circulating PTH for adult rats assayed with this IRMA are in the range 10–15 pg/ml, and of the same order of magnitude as published values for biologically active PTH. The standard curve for the IRMA was linear over the range 3.4–240 pg/ml of rPTH 1–34, and serum samples diluted in parallel with the standard curve. The within-assay and between-assay coefficients of variation ranged from 5.2% ( n=18) to 7.6% ( n=24) and 8.3% ( n=16) to 26.4% ( n=10), respectively. Serum PTH values (mean±S.E.) for parathyroidectomized rats were 3.5±0.6 pg/ml ( n=18) versus 10.3±1.4 pg/ml ( n=16) for intact non-mated rats. Calcium injections suppressed circulating PTH by 50%. Lactating rats had serum PTH levels 5-fold higher and vitamin D deficient rats 60-fold higher than non-mated controls. PTH secreted from parathyroid cells in vitro was in the range 60–490 pg/ml as determined by the IRMA. These values represented 86.0±9.0% of the comparable bioassay values, indicating that the IRMA detects only bioactive PTH.
ISSN:0169-6009
DOI:10.1016/S0169-6009(08)80214-0