MEMBRANE ION-TRANSPORT IN BARTTERS-SYNDROME - EVIDENCE FOR A NEW SYNDROME SUBTYPE

Fifteen patients with Bartter's syndrome (hyponatremic hypochloremic h ypokalemic metabolic alkalosis) were compared with 15 healthy voluntee rs. Red blood cell Na+/H+ and Cl-/HCO3- exchanges were enhanced in all patients with Bartter's syndrome. Ln calciuric normomagnesemic patien ts, sensitive to nonsteroidal anti-inflammatory drugs (classic Bartter 's syndrome), red blood cell Na+,K+,2Cl(-) cotransport was markedly re duced, calcium-dependent K+ permeability was moderately increased, and up to 60% of sodium permeability was represented by cAMP-activated fr action (presumably human analog of beta-isoform of Na+/H+ exchange). I n noncalciuric hypomagnesemic patients insensitive to indomethacin (Gi telman's syndrome), Na+,K-,2Cl(-) cotransport was enhanced, Na+ permea bility was increased due to calmodulin-dependent fraction, and calcium -dependent K+ permeability was markedly enhanced. A new subtype of Bar tter-like syndrome (''variant Bartter's syndrome'') has been described in which calciuria, hypomagnesemia, and insensitivity to nonsteroidal anti-inflammatory drugs were associated with decreased Na+,K+,2Cl(-) cotransport, enhanced calmodulin-activated fraction of Na+ influx, and reduced calcium-dependent K+ permeability.