Studies on the site of renal sodium loss in two patients with cystinosis. Effects of hydrochlorothiazide on tubular sodium reabsorptive mechanisms.

The purpose of this study was to examine the effect of hypotonic saline diuresis on two patients with cystinosis, trying to localize the site of renal sodium loss. At the same time, we have performed the same hypotonic saline infusion under hydrochlorothiazide administration. Results seem to prove the proximal tubular localization of the salt-wasting syndrome in cystinotic patients. On the other hand, these results suggest that hydrochlorothiazide effect can be related to the hypovolemia due to the distal tubular action of hydrochlorothiazide that could inhibit the 'third' natriuretic factor, thus increasing the proximal tubular sodium reabsorption.