Abstract
ABSTRACT Hypocalcemic activity in human urine is labile, especially when the pH of the urine is less than 5. At pH 4.0 and below, essentially all endogenous or added hypocalcemic activity is lost during incubation at room temperature for 1 hr. Inactivation can be prevented by boiling the urine at pH 5–7 before acidification. A simple method has been developed for concentrating hypocalcemic activity from the urine of patients with medullary carcinoma of the thyroid gland. The procedure involves adsorption of the activity on powdered silica (Quso G-32, 4 C, pH 5–7), heating in a boiling water bath, and elution of the active material with 2% acetic acid-20% acetone. The final product is assayed biologically in rats. The biologically active fraction is inactivated by pepsin, trypsin and ashing; it gives log dose-response lines in the bioassay which are linear and parallel to the MRC standard; and it elutes from Sephadex in the same position as human tumor thyrocalcitonin and pure labeled synthetic calcitonin ...
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