BIOASSAY OF PARATHYROID HORMONE IN RATS BY DETERMINATION OF PLASMA CALCIUM, URINARY 32P EXCRETION AND SERUM ALKALINE PHOSPHATASE

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Abstract
SUMMARY: Methods for assay of parathyroid hormone based on an increase in serum calcium concentration, urinary 32P excretion and serum alkaline phosphatase elevation in parathyroidectomized rats have been compared and modifications introduced to improve sensitivity, precision, speed and ease of manipulation. Both the serum calcium and urinary 32P assay gave good precision (mean λ = 0·23 and 0·29, respectively) but by the serum calcium method less than 10 USP units of parathyroid hormone could not be detected, whereas the phosphaturic assay detects as little as 0·5 USP unit. Both assays are simple to perform and each requires only 2 days to complete. They can be combined in a single design using the same animals. Assays based on serum alkaline phosphatase levels in parathyroidectomized rats were not successful since it was impossible to produce a significant alteration in serum alkaline phosphatase by the administration of parathyroid hormone.