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Department of Molecular Medicine, Endocrine and Diabetes Unit, Karolinska Hospital and Institute, S-171 76 Stockholm, Sweden.
1
Department of Medicine, University of California, San
Diego and the San Diego VA Medical Center, La Jolla, CA 91261.
a Address correspondence to this author at: Department of Molecular Medicine, The Endocrine and Diabetes Unit, Karolinska Hospital, L1:02, S-171 76 Stockholm, Sweden. Fax 46-8-30 34 58; email bucht{at}enk.ks.se
We recently developed a two-site immunofluorometric assay (IFMA) of salmon calcitonin (SCT) by DELFIA (dissociation enhancement lanthanide fluoroimmunoassay) technique using the same polyclonal antibodies both for "catching" the antigen and for signaling. In the present study we used a monoclonal antibody to SCT 111 as the capture antibody. This antibody was biotinylated before use in streptavidin-coated microtitration plates. The polyclonal antibody labeled with Eu chelate was used as a signaling marker. This combination of antibodies resulted in an assay that was three to four times more sensitive than the previous IFMA, with a detection limit of 0.3 pmol/L serum. Intact SCT 132 was detected by the assay (recoveries 9496%), but not the fragments SCT 111 and SCT 1032 or human calcitonin. Dilutions of plasma samples containing SCT were parallel to the calibration curve of SCT 132. Pharmacokinetic studies of SCT, 100 IU administered intramuscularly to 10 men, indicated peak serum concentrations of 32128 pmol/L within 1020 min with apparent half-life of 56 ± 18 min (mean ± SD). This new assay will allow study of the pharmacokinetics of new calcitonin preparations that do not require injection.
Key Words: indexing terms: fluorometry lanthanide
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