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Research Article Free access | 10.1172/JCI105644
Department of Medicine, Harvard Medical School, Boston, Massachusetts
Department of Medicine, Beth Israel Hospital, Boston, Massachusetts
‡Recipient, U. S. Public Health Service Career Development Award 7-K3-HE-12-113-03.
Address requests for reprints to Dr. Philip R. Steinmetz, Beth Israel Hospital, 330 Brookline Avenue, Boston, Mass. 02215.
*Received for publication 8 February 1967 and in revised form 12 June 1967.
Supported by grants from the William F. Milton Fund of Harvard University, the American Heart Association, and a General Research Support Grant, 5S01 FR05479-04, from the U. S. Public Health Service.
Presented in part before the annual meeting of the American Society for Clinical Investigation, 1 May 1966, Atlantic City, N. J. (1).
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Published October 1, 1967 - More info
The mechanism of acidification by the urinary bladder of the water turtle was studied in an in vitro system which permitted control and measurement of electrical and concentration driving forces. The rate of hydrogen ion secretion was measured by means of a pH stat technique in the absence of exogenous carbon dioxide and bicarbonate.
Transport of hydrogen ion into the solution bathing the mucosal surface of the bladder was associated with the appearance of alkali in the serosal compartment. The mean rate of hydrogen ion secretion in the absence of electrical and concentration gradients across the bladder was 0.96 μmole/hr. The secretion rate was only slightly greater in the presence of the spontaneous potential difference. The maximal hydrogen ion gradient that could be generated by the bladder was 3.33 pH units in the presence of the spontaneous voltage and 3.02 pH units in the short-circuited state.
Hydrogen ion secretion was markedly reduced by acetazolamide and anaerobiosis, which indicated that under our experimental conditions acidification depended on the production and enzymatic hydration of metabolic carbon dioxide. On the basis of the stoichiometry of the pH changes across the membrane under different conditions, it is suggested that the active transport mechanism for hydrogen ion is located near the mucosal surface of the epithelial cell and that the alkali generated in back of the pump moves passively into the serosal fluid along an electrochemical gradient.