Cell membrane water permeability of rabbit cortical collecting duct

Abstract

The water permeability (P _osm) of the cell membranes of isolated perfused rabbit cortical collecting ducts was measured by quantitative light microscopy. Water permeability of the basolateral membrane, corrected for surface area, was 66 μm·sec⁻¹ for principal cells and 62.3 μm·sec⁻¹ for intercalated cells. Apical membraneP _osm values corrected for surface area, were 19.2 and 25 μm·sec⁻¹ for principal and intercalated cells, respectively, in the absence of antidiuretic hormone (ADH). Principal and intercalated cells both responded to ADH by increasingP _osm of their apical membranes to 92.2 and 86.2 μ·sec⁻¹ respectively. The ratio of the total basolateral cell membrane osmotic water permeability to that of the apical cell membrane was ∼27∶1 in the absence of ADH and ∼7∶1 in the presence of the hormone for both cell types. This asymmetry in water permeability is most likely due to the fact that basolateral membrane surface area is at least 7 to 8 times greater than that of the apical membrane. Both cell types exhibited volume regulatory decrease when exposed to dilute serosal bathing solutions. Upon exposure to a hyperosmotic serosal bath (390 mosm), pricipal cells did not volume regulate while two physiologically distinct groups of intercalated cells were observed. One group of intercalated cells failed to volume regulate; the second group showed almost complete volume regulatory increase behavior.