Direct evidence for the absence of active Na+ reabsorption in hamster ascending thin limb of Henle's loop.

AUTOR(ES)

Kondo, Y

RESUMO

The mechanisms of Na+ transport across cell membranes were investigated in the in vitro microperfused hamster ascending thin limb (ATL) of Henle's loop using a fluorescent Na+ indicator sodium-binding benzofuran isophthalate. The intracellular Na+ concentration ([Na+]i) of the ATL cells was 17.1 +/- 1.7 mM (n = 22) when the ATL was microperfused in vitro with Hepes-buffered solution containing 204 mM Na+. Elimination of metabolites such as glucose and alanine from the basolateral solution increased [Na+]i. Applying either 5 mM cyanide or 5 mM iodoacetic acid to the bath also increased [Na+]i. The elimination of K+ and the addition of 10(-4) M ouabain in the bath increased [Na+]i by 25.0 +/- 5.0 mM (n = 5) in 3 min and by 10.7 +/- 2.4 mM (n = 4), respectively. The elimination of luminal and basolateral Na+ resulted in a decrease in [Na+]i, indicating Na+ permeability of both the luminal and basolateral cell membranes. The luminal Na+ permeability was not affected by furosemide. The presence of luminal Na+ permeability and the basolateral Na+/K+ ATPase suggests the presence of net active reabsorption of Na+, which is not a physiologically important amount, in our estimation.

Documentos Relacionados

• Evidence for conductive Cl- pathways across the cell membranes of the thin ascending limb of Henle's loop.
• Vasopressin stimulates Cl- transport in ascending thin limb of Henle's loop in hamster.
• Cell volume regulation by the thin descending limb of Henle's loop.
• Cellular heterogeneity of ammonium ion transport across the basolateral membrane of the hamster medullary thick ascending limb of Henle's loop.
• Effect of vasopressin on electrical potential difference and chloride transport in mouse medullary thick ascending limb of Henle's loop.