Radioimmunoassay of urinary antidiuretic hormone with application to study of the Brattleboro rat.

Abstract

A sensitive and specific radioimmunoassay for antidiuretic hormone (ADH) has been applied to the measurement of ADH excreted in the urine. ADH is extracted from urine and concentrated using cation exchange chromatography, with mean recovery through the procedure of 89.4% for 125I-LVP and 98.5% for unlabeled AVP. Urine specimens were collected from Long-Evans rats and rats of the Brattleboro strain which were either heterozygous or homozygous for diabetes insipidus (DI). Immunoassay and antidiuretic bioassay performed on aliquots of the same urine specimens were in excellent agreement. Under conditions of ad lib. fluid and food intake, mean urinary excretion of immunoreactive material was 4.5 mU/24 hr in normal rats, 2.3 mU/24 hr in heterozygous DI rats and 0.16 mU/24 hr in homozygous DI rats. There was a positive relationship between urinary ADH excretion and urine concentration and an inverse relationship between urinary ADH excretion and urine volume. During water deprivation, normal rats promptly incre...