Renal potassium adaptation: role of the Na+-K+ pump in rat cortical collecting tubules
Fujii, Y.; Mujais, S.K.; Katz, A.I.
American Journal of Physiology 256(2 Pt 2): F279-F284
1989
ISSN/ISBN: 0002-9513 PMID: 2537024 Document Number: 329543
To evaluate the mechanism of renal potassium adaptation several facets of Na+-K+-ATPase function were studied during K loading in rat cortical collecting tubule (CCT). Urinary K excretion increased within the 1st day after initiation of loading of diet to a value matching intake, indicating the early onset of K adaptation. CCT Na+-K+-ATPase activity after 1 and 2 days on the high-K diet was not different from that observed in controls, whereas it increased to threefold baseline after 7 days. Specific binding of ouabain was unchanged by 2 days of high-K diet, but was increased on the 7th day. There was an early increase in rubidium uptake that persisted throughout the period of observation. Acute (60 min) KCl infusion into control rats caused a significant increase in Rb uptake, whereas Na+-K+-ATPase hydrolytic activity remained unchanged. In isolated perfused kidney, increasing perfusate K caused an increase in CCT Rb uptake similar to that observed in vivo, again without altering the hydrolytic activity of the enzyme.