[New method for the quantitative determination of antidiuretic hormone in the plasma]

Having in mind that ADH affects reapsorption of osmoticaly free water the authors examined urine diuresis together with its osmolality in 85 recipient rats. The animals endured water loading of 5% of their body weight by means of stomach lavages twice at 45 minutes intervals for a period of 3 days. Vena jugularis was cannulated under narcosis with heparinized polyethylene catheter, which was attached to the skull by means of a special socle. The training water loading continued two more days, after which AD activity or a standard solution of ADH was tested. Urine was collected every 15 minutes for a period of 120 minutes and its volume and osmolatily was determined. 0.2 ml of saline, standard or plasma, prepared for removal of nonspecific antidiuretic activity was administered on the 30th minute of the second water loading. There was a linear dependence between osmolality of urine and the administered amount of ADH. A standard curve of the ratio osmolality/microunits of ADH was prepared. The values of osmolality, obtained during administration of plasma were compared with those of the standard curve and the amount of ADH was determined in microunits. The method assures quantitative determination of ADH in values pover 10 microunits, which are obtained in animals after experimental affects and in some diseases of persons.