Effect of Experimental Salt Depletion and Aldosterone Load on Sodium and Chloride Concentration in the Sweat of Patients with Cystic Fibrosis of the Pancreas and of Normal Children.

Aldosterone plays an important part in the regulation of the extracellular volume. It is known today that this corticosteroid influences not only the tubular reabsorption of sodium in the kidneys, but also intervenes in the sodium elimination mechanism of the sweat glands (Siegenthaler, de Haller, Veyrat and Muller, 1962). The study of the renal and extrarenal effect of aldosterone is best accomplished by experimental salt depletion, produced by a strict salt-free diet. Fig. 1 shows the variations of some parameters such as weight, natriuresis, sodium and chloride concentration in sweat, and urinary aldosterone, as observed in the course of saline depletion produced in a young healthy adult. The salt loss is precipitated by administration of a saliuretic substance (chlorthalidone) on the first and second day of the diet. Under these conditions the weight, as well as the urinary sodium excretion, decrease rapidly and progressively to a minimum on the fourth day. At the same time there is an important fall in the sweat sodium and chloride concentration, expressed in mEq per litre. As for the urinary aldosterone it increases noticeably reaching very high levels at the end of the test. Method In our experiments, perspiration was provoked by iontophoresis with 0 2% pilocarpine nitrate on the forearms of children and on the abdominal wall of small infants (Gibson and Cooke, 1959). The electrolytes were determined directly in the sweat by micromethod. Sodium was measured by flame photometry and chloride according to Schales and Schales (1941),