Biotinylation of γENaC. Kidneys from rats on a low-Na diet were perfused with or without biotin. Lanes were loaded with 40 μg of total membrane protein or 20 μl of eluate from the neutravidin beads. Total membranes from whole kidney had two predominant stained bands at ∼85 and ∼65 kD. Staining of the lower but not the higher molecular mass band was observed in eluates from biotinylated kidneys. No staining was detected in eluates from nonbiotinylated kidneys.