Presence of a natriuretic factor in urine of normal men undergoing water immersion.

Presence of a natriuretic factor in urine of normal men undergoing water immersion. Immersion of normal subjects in water to the neck (NI) results in a redistribution of blood volume, relative central hypervolemia, and a significant natriuresis which is equal in magnitude to that produced by 10% expansion of the extracellular fluid volume by isotonic saline. The natriuresis of NI is independent of changes in GFR and is not prevented by the administration of DOCA. The present study was undertaken to determine whether the NI natriuresis is associated with increased activity of the natriuretic factor (NF) that has been observed in volume-expanded dogs and uremic dogs and patients. Twelve normal subjects were studied following overnight water restriction for 10 hr. Each subject was studied under control conditions, during NI in the seated position, and at the same time of day. U Na V, while remaining constant during control studies, increased significantly during NI. Bioassays for natriuretic activity were performed in rats by using urine fractions from NI and control studies. The NI fractions in the test animals resulted in significant increments in both U Na V (1.27 ± 0.28µEq/min) and FE Na (1.39 ± 0.21%) (P Na V, and there was a small increment in FE Na (0.70 ± 0.25%; P Presence d'un facteur natriuretique dans l'urine de sujets normaux soumis a l'immersion. L'immersion de sujets normaux jusqu'au cou (NI) a pour consequence une redistribution du volume sanguin, une hypervolemie centrale relative et une natriurese significative qui est egale, en importance, a celle produite par une expansion de 10% du volume des liquides extracellulaires au moyen de solute sale isotonique. La natriurese de NI est independante des modifications du debit de filtration glomerulaire et n'est pas empechee par l'administration prealable de DOCA. Ce travail a pour but de savoir si la natriurese d'immersion est associee a une augmentation de l'activite du facteur natriuretique (NF) telle qu'elle a ete observee chez des chiens soumis a une expansion ou des hommes ou des chiens uremiques. Douze sujets normaux ont ete etudies apres 10 hr de suppression des boissons. Chaque sujet a ete etudie dans des conditions controles et pendant la NI, en position assise et au meme moment de la journee. U Na V augmente significativement pendant la NI alors qu'il etait constant pendant les periodes controles. Le dosage biologique de l'activite natriuretique a ete realise chez des rats, a partir des fractions de l'urine recueillie pendant NI et pendant les periodes controles. Les fractions provenant de NI ont eu pour effet une augmentation significative de U Na V (1,27 ± 0,28µEq/min) et FE Na (1,39 ± 0,21%) chez les animaux utilises. Les fractions controles n'ont pas eu d'effet significatif sur U Na V et ont determine une nette augmentation de FE Na (0,7 ± 0,25%; P

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