Distribution and Half-life of131I-Labeled Parathyroid Hormone in the Rat1

Abstract

The half-life and volume of distribution of radioiodinated parathyroid hormone was measured in normal and parathyroidectomized rats. The labeled hormone was detected in plasma by modified paper electrophoresis and further identified by reaction with specific antiparathyroid hormone antibody. The half-life of the labeled hormone was 22.3 min. in normal rats, 24.3 min. in parathyroidectomized rats and 27.6 min. in parathyroidectomized rats given excess carrier parathyroid hormone. The volumes of distribution for the hormone in the 3 groups were 36.4, 27.0 and 28.6% of the body weight, respectively. The data obtained support the conclusion, derived from physiological experiments, that circulating parathyroid hormone is rapidly destroyed.