Sodium-potassium ATPase activity mediates cyst formation in metanephric organ culture

To study the possible role of altered transtubular transport in renal tubular cyst formation, the ontogeny of renal Na-K ATPase was studied during glucocorticoid-induced cystic metanephric tubular development in serum-free, murine organ culture (SFMOC). Utilizing an enzyme-linked kinetic microassay, a developmental profile of total ATPase and specific Na-K ATPase activity was established for control (CON) and glucocorticoid-induced cystic organ culture (CY) explants. During 120 hr of CON and CY organ culture nephrogenesis total Na-K ATPase activity, specific Na-K ATPase activity, and the Na-K ATPase: total ATPase ratio progressively increased, simulating normal in vivo murine enzyme development. However, from 48 to 120 hr of organ culture, CY showed significant increases in Na-K ATPase activity when compared to CON at similar stages of development. Na-K ATPase activity (expressed as nmoles . min-1 . mg protein -1, mean +/- SD) was, at: 48 hr, CY 13.1 +/- 0.7 vs. CON 11.0 +/- 0.9 (P less than 0.01); 72 hr, CY 16.4 +/- 1.1 vs. CON 12.2 +/- 0.7 (P less than 0.001); 96 hr, CY 35.4 +/- 4.9 vs. CON 13.7 +/- 0.4 (P less than 0.001); and 120 hr, CY 26.1 +/- 1.4 vs. CON 16.3 +/- 0.9 (P less than 0.001). The initial differences in CY enzyme activity preceded the earliest ultrastructural evidence of cyst formation by 18 to 24 hr, while subsequent increases in Na-K ATPase activity in CY paralleled progressive tubular cyst formation. Tubular cyst formation in CY could be largely prevented by daily incubation of explants with ouabain, 0.2 mM (final concentration) X 120 min, without deleterious effects on overall metanephric development.(ABSTRACT TRUNCATED AT 250 WORDS)