Figure 5.

Na⁺,K⁺-ATPase expression and activity varies in parallel with apical Na⁺ delivery in rat CCD. Rats were subcutaneously implanted with an osmotic minipump delivering aldosterone for 7 days. After 3 days of low sodium diet, rats were separated into two groups and given either low sodium diet (L) or normal sodium diet (N) for 4 additional days. Rats were then euthanized and CCD were isolated by microdissection from collagenase-treated kidneys. Na⁺,K⁺-ATPase α-subunit expression was assessed by Western blot on pools of 50 CCDs and Na⁺,K⁺-ATPase hydrolytic activity was determined by a radiochemical assay in isolated CCD. Results show that increased Na⁺ entry following reintroduction of sodium in the diet is associated with increased Na⁺,K⁺-ATPase abundance and activity in CCD.