Stimulation of calcitonin secretion by calcium receptor activators: Evaluation using a new, highly sensitive, homologous immunoradiometric assay for rat calcitonin

Jeffrey R. Lavigne, Richard J. Zahradnik, Rebecca L. Conklin, Lyssa D. Lambert, Mary A. Logan, Ashutosh Parihar, John Fox

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Current rat calcitonin immunoassays use human calcitonin antisera, and suffer from poor sensitivity, long incubation periods, nonspecific interferences, and unreliability. The homologous immunoradiometric assay (IRMA) for rat calcitonin described here overcomes these problems. Overnight incubation yields a detection limit of 0.4 pg/mL, a standard curve that is linear to >1800 pg/mL, and intra- and interassay coefficients of variation of <7%. Gel filtration chromatography of rat plasma and rat medullary thyroid carcinoma 44-2 cell media showed that the vast majority of immunoreactivity coeluted with calcitonin standard. In 44-2 cells, increasing extracellular Ca 2+ concentration or incubation with the calcimimetic compound NPS R-467 markedly increased calcitonin secretion. Plasma calcitonin levels were elevated in rats anesthetized with ketamine/xylazine and in conscious rats with chronic renal insufficiency. Calcitonin levels decreased following EGTA- induced hypocalcemia and were undetectable after thyroparathyroidectomy. In normal conscious rats, plasma calcitonin levels averaged 3-5 pg/mL and increased up to 100-fold following calcium (Ca) infusion or NPS R-467 administration. The assay also quantified calcitonin in plasma of normal and Ca-injected mice. This assay has revealed that plasma calcitonin levels in normal rats are much lower than the detection limits of most existing assays, but can increase by 100-fold on activation of the C-cell Ca 2+ receptor.

Original languageEnglish (US)
Pages (from-to)293-301
Number of pages9
JournalEndocrine
Volume9
Issue number3
DOIs
StatePublished - Dec 1 1998

Keywords

  • Calcimimetics
  • Calcitonin
  • Immunoradiometric assay
  • Rat
  • Rat medullary thyroid carcinoma 44-2 cells

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Endocrinology

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