Thyrocalcitonin: Parameters of Bio-assay1

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Abstract
A simplified rat bio-assay for thyrocalcitonin has been developed. Use of the subcutaneous route of administration and a fluorometric Ca analysis have increased the speed and convenience of the assay procedure as compared to published methods, without loss of precision. The assay gave parallel dose response curves for 2 partially purified thyrocalcitonin standard preparations, a House Standard and the Medical Research Council (MRC) Standard A, and negative response to a number of potential hypocalcemic agents. In studies of factors which might affect assay response it was found that: fasting rats prior to assay increased sensitivity, injection volumes, per 100 g body weight, of 0.5 and 1.0 ml gave comparable responses, while the 0.1 ml volume gave a lesser response, male Holtzman and CFE rats appeared to be equally sensitive to thyrocalcitonin, whereas CFE female rats were less responsive, hypertonic solutions of NaCl and KCl gave no significant change in plasma Ca level although PO4 lowered Ca, and at an injection volume of 1 ml/100 g, gelatin vehicle in excess of 7.5%. appears to prolong the effect of high doses of thyrocalcitonin.