ELECTROLYTE ENVIRONMENT MODULATES DIFFERENTIATION IN EMBRYONIC RENAL COLLECTING DUCT EPITHELIA

The influence of electrolytes on the development of renal principal an d intercalated collecting duct cells is unknown. Consequently embryoni c collecting duct epithelia were exposed to different electrolyte conc entrations, and their degree of differentiation was registered by immu nohistochemical methods. Embryonic collecting duct epithelia were isol ated from neonatal rabbit kidneys and placed on tissue carriers. The a pical urine and the basal serum compartments were simulated in a gradi ent culture container. The two sides of the epithelium were each const antly superfused with medium for 13 days. In controls the medium on bo th apical and basal side was standard Iscove's modified Dulbecco's Med ium (IMDM) with 112 mmol/l Na+ and 85 mmol/l Cl-. In experimental seri es the NaCl concentration at the basal side of the epithelium was incr eased up to 137 mmol/l Na+ and 99 mmol/l Cl- as found in the serum of neonatal rabbits. Light microscopy revealed morphologically faultless epithelia following gradient perfusion culture in standard and NaCl-ad apted IMDM. The development of principal and intercalated cell feature s was monitored with the monoclonal antibodies 703, 503, P(CD)9, and p eanut lectin. Cells immunopositive for monoclonal antibody 703, for ex ample, increased from less than 10% in controls to more than 80% in Na Cl-adapted IMDM. It is a new finding that the development of collectin g duct cell features is influenced by the extracellular electrolyte en vironment.