Ouabain-insensitive K-adenosine triphosphatase in distal nephron segments of the rabbit.

Abstract

An electrogenic H-ATPase sensitive to inhibition by N-

Mineralocorticoids and acidosis regulate H+/HCO3- transport of intercalated cells.

“…Similar observations were described in S3 proximal tubule (33), OMCDo intercalated cells (6), and OMCDi (8). Recently the presence of H+-K+-ATPase, another H+ pump, has been suggested in OMCDi (29)(30)(31). This ATPase was insensitive to ouabain (29,30) but was inhibited by vanadate (29,30), and, more specifically, also by omeprazole (29)(30)(31) and SCH28080 (8,30).…”

“…Recently the presence of H+-K+-ATPase, another H+ pump, has been suggested in OMCDi (29)(30)(31). This ATPase was insensitive to ouabain (29,30) but was inhibited by vanadate (29,30), and, more specifically, also by omeprazole (29)(30)(31) and SCH28080 (8,30). In this study, we tested the effects of omeprazole and SCH28080 on the pHi recovery.…”

“…pHi was measured in cells at the side of tubules in this study. After an equilibration period of [20][21][22][23][24][25][26][27][28][29][30] (6,26). This maneuver is favorable for pHi measurement of intercalated cells because the interference from neighboring principal cells is small (6).…”

Mineralocorticoid modulation of apical and basolateral membrane H+/OH-/HCO3- transport processes in the rabbit inner stripe of outer medullary collecting duct.

“…Previously, we have found that chronic DOCA treatment does not significantly alter rabbit muscle K+ content (unpublished observations) and recently, Garg (27) found no increase in H+-K+-ATPase activity in the rabbit medullary collecting duct after chronic DOCA treatment. This is in contrast to the marked elevation ofH+-K+-ATPase activity they found in the medullary collecting duct under conditions of K+ deficiency (28). Thus, Na+-independent pHi recovery from an induced acid load under conditions of mineralocorticoid excess most likely represents a vacuolar H + pump.…”

Active proton secretion and potassium absorption in the rabbit outer medullary collecting duct. Functional evidence for proton-potassium-activated adenosine triphosphatase.

“…At physiologic flow rates these changes in K-absorptive flux would significantly influence the rate of renal K excretion (5). Moreover, the recent demonstration of ouabain-insensitive, omeprazole-sensitive, potassium-activated adenosine triphosphatase (K-ATPase) activity in the CD (6)(7)(8) that is increased in activity in the OMCDi with K depletion (7) provides further indirect evidence that K absorption may proceed via a primary active, luminal K-absorptive pump. Thus, the present study was de-signed to examine the role of proton-potassium-activated adenosine triphosphatase (H-K-ATPase) on proton secretion and K absorption in the OMCDi.…”