title: A new rapid and reproducible homologous immunoradiometric assay for amino-terminal parathyroid hormone in the rat.
abstract: Measurement of parathyroid hormone (PTH) in the rat is most often performed with competitive ligand radioimmunoassays (RIA) utilizing heterologous antibodies. We report here the validation of a newly developed homologous immunoradiometric assay (IRMA) for rat PTH. Two different goat antibodies to the amino-terminal sequence of rat PTH are utilized; one is immobilized onto plastic beads to capture the PTH molecules and the other is radiolabeled for detection. To test this new IRMA, 30 Sprague-Dawley rats were randomized into three treatment groups to receive by intraperitoneal injection: (1) saline 1 ml/kg (control); (2) calcium chloride 40 mg/kg (hypercalcemic); and (3) EDTA 300 mg/kg (hypocalcemic). Blood samples were taken at 0, 30, 60, 180, and 300 minutes after administration of the assigned treatment for measurement of ionized calcium (Ca2+) and serum PTH. Most of the variance in PTH levels was found to be due to changes in Ca2+ (r2 = 0.780, P < 0.0001). There was also a close temporal relationship between the two, with the highest levels of PTH occurring at the same measured time points as the lowest Ca2+, and vice versa. The measured detection limit of the IRMA was 3 pg/ml with intra- and interassay coefficients of variation of 1.74% and 3.07%, respectively. Serial dilutions with pooled rat serum, synthetic rat PTH-(1-34), and synthetic human PTH-(1-34) showed good parallelism with increased specificity for the pooled and synthetic PTH, despite a degree of crossreactivity with hPTH.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Division of Endocrinology and Metabolism, Albert Einstein Medical Center, Philadelphia, Pennsylvania 19141, USA.
authors.forename: B
authors.initials: B
authors.lastname: Rucinski
authors.forename: G N
authors.initials: GN
authors.lastname: Mann
authors.forename: S
authors.initials: S
authors.lastname: Epstein
mesh_terms: D000818:Animals; D002118:Calcium / Q000097:blood; D002122:Calcium Chloride / Q000494:pharmacology; D003429:Cross Reactions; D004492:Edetic Acid / Q000494:pharmacology; D005069:Evaluation Studies as Topic; D006801:Humans; D015592:Immunoradiometric Assay / Q000379:methods* / Q000706:statistics & numerical data; D008297:Male; D010281:Parathyroid Hormone / Q000097:blood* / Q000276:immunology; D010446:Peptide Fragments / Q000097:blood* / Q000276:immunology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000032:analysis / Q000276:immunology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D019379:Teriparatide
chemical_list: D010281:Parathyroid Hormone; D010446:Peptide Fragments; D011994:Recombinant Proteins; D019379:Teriparatide; D004492:Edetic Acid; D002122:Calcium Chloride; D002118:Calcium