Abstract
The unidirectional fluxes of sodium, chloride, and of the bicarbonate and CO2 pair were determined across the isolated large intestine of the bullfrog, Rana catesbiana. The isolated large intestine of the frog is characterized by a mean transmembrane potential of 45 mv., serosal surface positive with respect to mucosal. The unidirectional sodium flux from mucosal to serosal surface was found to be equal to the short-circuit current, thus the net flux was less than the simultaneous short-circuit current. This discrepancy between active sodium transport and short-circuit current can be attributed to the active transport of cation in the same direction as sodium and/or the active transport of anion in the opposite direction. The unidirectional fluxes of chloride and the bicarbonate and CO2 pair revealed no evidence for active transport of either anion. A quantitative study of chloride fluxes at 45 mv. revealed a flux ratio of 1.8 which is considerably less than a ratio of 6 expected for free passive diffusion. It was concluded that a considerable proportion of the isotopic transfer of chloride could be attributed to "exchange diffusion." Study of the electrical properties of the isolated frog colon reveals that it can be treated as a simple D. C. resistance over the range of -20 to +95 mv.
Full Text
The Full Text of this article is available as a PDF (725.5 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- COTLOVE E., TRANTHAM H. V., BOWMAN R. L. An instrument and method for automatic, rapid, accurate, and sensitive titration of chloride in biologic samples. J Lab Clin Med. 1958 Mar;51(3):461–468. [PubMed] [Google Scholar]
- D'AGOSTINO A., LEADBETTER W. F., SCHWARTZ W. B. Alterations in the ionic composition of isotonic saline solution instilled into the colon. J Clin Invest. 1953 May;32(5):444–448. doi: 10.1172/JCI102757. [DOI] [PMC free article] [PubMed] [Google Scholar]
- DURBIN R. P., HEINZ E. Electromotive chloride transport and gastric acid secretion in the frog. J Gen Physiol. 1958 May 20;41(5):1035–1047. doi: 10.1085/jgp.41.5.1035. [DOI] [PMC free article] [PubMed] [Google Scholar]
- HOGBEN C. A. Active transport of chloride by isolated frog gastric epithelium; origin of the gastric mucosal potential. Am J Physiol. 1955 Mar;180(3):641–649. [PubMed] [Google Scholar]
- LEAF A., ANDERSON J., PAGE L. B. Active sodium transport by the isolated toad bladder. J Gen Physiol. 1958 Mar 20;41(4):657–668. doi: 10.1085/jgp.41.4.657. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Redman T., Willimott S. G., Wokes F. The p(H) of the Gastro-intestinal Tract of Certain Rodents used in Feeding Experiments, and its Possible Significance in Rickets. Biochem J. 1927;21(3):589–605. doi: 10.1042/bj0210589. [DOI] [PMC free article] [PubMed] [Google Scholar]