Document Detail

Omeprazole and SCH 28080 inhibit acid secretion by the turtle urinary bladder.
MedLine Citation:
PMID:  7694339     Owner:  NLM     Status:  MEDLINE    
There is now convincing evidence that in addition to the vacuolar-type H(+)-ATPase, a gastric-type H+/K(+)-ATPase participates in acidification by the distal nephron. To determine whether a similar pump exists in the turtle bladder, we examined the dependence of acid secretion on mucosal K+, and the effects of supposedly specific inhibitors of the gastric H+/K(+)-ATPase, omeprazole and SCH 28080. In CO2-stimulated bladders both drugs produced dose-dependent inhibition of electrogenic H+ secretion measured as the reverse short-circuit current (RSCC). At the highest concentrations tested, H+ secretion decreased 45 +/- 16% with mucosal and 20 +/- 7% with serosal omeprazole (P < 0.01). SCH 28080 at 400 microM produced essentially complete inhibition of H+ secretion with either mucosal or serosal application. When H+ secretion was purposefully inhibited by DIDS or an adverse mucosal pH gradient, SCH 28080 had no effect on RSCC. Removing mucosal K+ (measured K+ < 50 microM), with or without mucosal barium, had no effect on RSCC. The inhibition of RSCC by omeprazole was reversed by mercaptoethanol. Finally, HCO3 secretion, as measured by either RSCC or pH-stat titration, increased significantly in response to 400 microM SCH 28080. The results demonstrate that these compounds inhibit acid secretion by the turtle bladder but stimulate the secretion of base. In view of the total independence of acid secretion on potassium, it is unlikely that any of the bladder's acid secretion is mediated by an H+/K(+)-ATPase. The most reasonable interpretation of the data is that omeprazole and SCH 28080, previously thought to be specific inhibitors of the H+/K(+)-ATPase, also inhibit the vacuolar H(+)-ATPase of the turtle bladder. The results also indicate that HCO3 secretion by the bladder employ a different mechanism of H+ transport than is used for acid secretion; there is no simple reversal of polarity in the acid- versus base-secreting cells.
M L Graber; P Devine
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Renal physiology and biochemistry     Volume:  16     ISSN:  1011-6524     ISO Abbreviation:  Ren. Physiol. Biochem.     Publication Date:    1993 Sep-Oct
Date Detail:
Created Date:  1993-11-26     Completed Date:  1993-11-26     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8906670     Medline TA:  Ren Physiol Biochem     Country:  SWITZERLAND    
Other Details:
Languages:  eng     Pagination:  257-67     Citation Subset:  IM    
Division of Nephrology, VAMC, Northport, N.Y. 11768.
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MeSH Terms
Bicarbonates / metabolism
Carbon Dioxide / pharmacology
H(+)-K(+)-Exchanging ATPase / antagonists & inhibitors,  metabolism
Hydrogen-Ion Concentration
Imidazoles / pharmacology*
Mercaptoethanol / pharmacology
Mucous Membrane / drug effects,  secretion
Omeprazole / pharmacology*
Potassium / physiology
Turtles / physiology*
Urinary Bladder / drug effects,  secretion*
Reg. No./Substance:
0/Bicarbonates; 0/Imidazoles; 0/Protons; 124-38-9/Carbon Dioxide; 60-24-2/Mercaptoethanol; 73590-58-6/Omeprazole; 7440-09-7/Potassium; 76081-98-6/Sch 28080; EC ATPase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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