COMPARISON BETWEEN THE BIOASSAY AND RADIOIMMUNOASSAY OF CALCITONIN IN PLASMA OF SEVERAL SPECIES

Abstract
A radioimmunoassay for porcine calcitonin (CT) has been described (Lequin, Hackeng & Schopman, 1969) which has a sensitivity of 10 pg./0·5 ml. incubate. With this assay the immunological activity of CT has now been measured in samples of thyroid venous plasma from pigs (1442, 2153 and 4141) taken at different times during continuous stimulation of CT release from the thyroid by hypercalcaemia. In another pig (2210), porcine CT was injected i.v. to raise the systemic plasma concentration of CT. Sample aliquots were bioassayed according to Leggate, Care & Frazer (1969). In the immunoassay a synthetic porcine CT α1–32 preparation (CT-s) was used for iodination with 125I and also to provide the standard curve. In three separate experiments it was found that CT-s had an immunological activity of 129 (114–147; 95% fiducial limits) immunological MRC units/mg. when compared with the MRC standard B to which, by definition, was assigned

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