Further observations on a low-molecular-weight natriuretic substance in the urine of normal man

Further observations on a low-molecular-weight natriuretic substance in the urine of normal man. Large quantities of the low-molecular-weight natriuretic material (F4), which appears after the salts when fractionated on G-25 Sephadex column, were obtained from the urine of normal man on a normal diet. The natriuretic substance in F4 was(1) ultrafiltrable through a membrane with a claimed molecular-weight cut-off of 500 daltons (Amicon UMO5);(2) soluble in more polar organic solvents;(3) totally soluble in 95% acetone when specific activity was doubled;(4) relatively resistant to heating at 100° C for 1 hour at a pH of 10, and to heating at 110° C in 6N hydrochloric acid for up to 90 hours under anaerobic conditions, and treatment with nitrous acid; it was less resistant to these procedures when extracted into 95% acetone;(5) not destroyed by trypsin, chymotrypsin, pronase, pepsin, leucine aminopeptidase, and subtilysin, nor was it destroyed by pepsin, leucine aminopeptidase, subtilysin, carboxypeptidase A and B, and aminopeptidase M, or by monoamine oxidase, aryl sulphatase, and β-glucuronidase when extracted into 95% acetone. The natriuretic substance in the 95% acetone-soluble F4 was totally destroyed by incubation with prolidase. The least amount of 95% acetone-soluble F4 required to produce a significant natriuresis in the bioassay rat was that derived from a 7-min sample of urine. The maximal response was obtained from a 30-min sample of urine. Continuous i.v. infusion of the 95% acetone-soluble F4 for 40min produced a sustained natriuresis, whereas a greater amount injected as a bolus produced an effect which was not sustained beyond 20min. Nouvelles observations relatives à une substance natriurétique de faible poids moléculaire dans l'urine humaine. De grandes quantités de substance natriurétique de faible poids moléculaire, qui apparaît après les sels au cours du fractionnement sur Sephadex G-25 (F4), ont été obtenues à partir de l'urine de sujets normaux soumis à un régime normal. La substance natriurétique en F4 est(1) ultrafiltrable à travers une membrane dont le point de coupure théorique est 500 daltons (Amicon UMO5);(2) soluble dans les solvants organiques les plus polaires;(3) totalement soluble dans l'acétone 95% quand l'activité spécifique est doublée;(4) relativement résistante au chauffage à 100° C pendant une heure à pH 10, an chauffage à 110° C dans HCl 6N jusqu'à 90 heures dans les conditions anaérobies, au traitement par l'acide nit