The pathogenesis of Bartter's syndrome. Functional and histologic studies.

We describe a patient with Bartter's snyndrome. In addition to the well-known characteristic findings by light microscopy, electron micrograms confirmed the presence of juxtaglomerular cell hyperplasia with polymorphous renin secretory granules and dense multivesicular bodies. Volume expansion by albumin infusion decreased plasma renin activity and aldosterone excretion, and improved the pressor response to exogenous angiotensin, suggesting that the renin-angiotensin-aldosterone system was not autonomous but that a decreased extracellular volume might be a major defect in this patient. During hypotonic saline diuresis, moreover, fractional free water clearance per fractional distal sodium delivery, CH2O/CH2O + CNa, was markedly depressed in the patient when compared with the value in the controls. Evidence presented suggests that chronic extracellular volume depletion exists as a consequence of an impaired sodium transport in the ascending limb of Henle's loop.