Abstract
1. Pieces of rabbit distal ileum, incubated for short periods of time in solutions containing tritiated amino acids, have been processed for autoradiography and the profiles of amino acid concentration across the villi determined by microdensitometry. 2. The concentration profiles of a series of amino acids could be described in terms of two descending exponentials, one extending from the brush border to the basal membrane of the enterocyte and the other from the base of the epithelial layer to the centre of the villus. 3. Exponential coefficients describing the steepness of these gradients were highest for basic amino acids. Coefficients for short-chain amino acids were greater than for long-chain neutral amino acids. None of these values changed for times of incubation varying from 5 to 180 sec. 4. Enterocytes accumulated amino acids in the apical cytoplasm, against a concentration gradient, within the first few seconds of incubation. This step-up in concentration decreased as the external concentration was increased, in a manner dependent on the amino acid used. 5. It is suggested that amino acid concentration gradients within enterocytes arise by diffusion and that the amino acid specificity of this process originates from an ability of the more lipophilic amino acids to permeate structures acting as barriers to the more hydrophilic molecules.
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Selected References
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- Dent C. E. A study of the behaviour of some sixty amino-acids and other ninhydrin-reacting substances on phenol-;collidine' filter-paper chromatograms, with notes as to the occurrence of some of them in biological fluids. Biochem J. 1948;43(2):169–180. [PMC free article] [PubMed] [Google Scholar]
- Hajjar J. J., Lamont A. S., Curran P. F. The sodium-alanine interaction in rabbit ileum. Effect of sodium on alanine fluxes. J Gen Physiol. 1970 Mar;55(3):277–296. doi: 10.1085/jgp.55.3.277. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Johnson I. T., Bronk J. R. Distribution of actively absorbed diffusible sugars in the jejunal epithelium of the rat. J Cell Sci. 1980 Oct;45:199–210. doi: 10.1242/jcs.45.1.199. [DOI] [PubMed] [Google Scholar]
- King I. S., Sepúlveda F. V., Smith M. W. Cellular distribution of neutral and basic amino acid transport systems in rabbit ileal mucosa. J Physiol. 1981;319:355–368. doi: 10.1113/jphysiol.1981.sp013913. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Klein R. A., Moore M. J., Smith M. W. Selective diffusion of neutral amino acids across lipid bilayers. Biochim Biophys Acta. 1971 Apr 13;233(2):420–433. doi: 10.1016/0005-2736(71)90339-7. [DOI] [PubMed] [Google Scholar]
- Munck B. G., Schultz S. G. Lysine transport across isolated rabbit ileum. J Gen Physiol. 1969 Feb;53(2):157–182. doi: 10.1085/jgp.53.2.157. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Paterson J. Y., Sepúlveda F. V., Smith M. W. Amino acid efflux from rabbit ileal enterocytes. J Physiol. 1982 Oct;331:537–546. doi: 10.1113/jphysiol.1982.sp014389. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Schultz S. G., Fuisz R. E., Curran P. F. Amino acid and sugar transport in rabbit ileum. J Gen Physiol. 1966 May;49(5):849–866. doi: 10.1085/jgp.49.5.849. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sepúlveda F. V., Smith M. W. Discrimination between different entry mechanisms for neutral amino acids in rabbit ileal mucosa. J Physiol. 1978 Sep;282:73–90. doi: 10.1113/jphysiol.1978.sp012449. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wolosewick J. J., Porter K. R. Microtrabecular lattice of the cytoplasmic ground substance. Artifact or reality. J Cell Biol. 1979 Jul;82(1):114–139. doi: 10.1083/jcb.82.1.114. [DOI] [PMC free article] [PubMed] [Google Scholar]