HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Buddington, R K Articles by Diamond, J Search for Related Content PubMed PubMed Citation Articles by Buddington, R K Articles by Diamond, J

Department of Physiology, University of California Medical School, Los Angeles 90024.

1. Herbivores have higher rates of intestinal sugar transport and lower rates of amino acid transport than carnivores, if each are studied while eating their respective natural diets. It was unclear whether these species differences involve a genetic contribution, since when omnivores are switched from a high-protein to a high-carbohydrate diet they reversibly increase sugar transport and suppress amino acid transport. Hence we studied eight fish species of differing natural diets while all were eating the same manufactured diet. 2. Na+-dependent L-proline uptake and active D-glucose uptake, measured in vitro by the everted intestinal sleeve technique, followed Michaelis-Menten kinetics. Values of the apparent Michaelis-Menten constant increased with values of the maximal transport rate, probably as a result of unstirred layer effects. 3. The ratio of proline to glucose uptake decreased in the sequence: carnivores greater than omnivores greater than herbivores. The intestine's uptake capacity for the non-essential nutrient glucose was much higher in herbivores than in carnivores, correlated with species differences in carbohydrate content of the natural diet. Proline uptake varied much less among species, since species with different natural diets still have similar protein requirements. 4. Since all species were studied while eating the same diet, these species differences in uptake are not phenotypic but genetic adaptations to the different natural diets. 5. In two fish species which normally switch from carnivory towards herbivory or omnivory as they mature, we observe a 'hard-wired' developmental change in intestinal uptake. Larger animals had lower proline uptake relative to glucose uptake than did smaller animals, even though both were being maintained on the same diet in the laboratory. 6. Carnivorous fish tend to allocate absorptive tissue to pyloric caeca or a thick mucosa, while herbivorous fish tend towards a long thin intestine.

This article has been cited by other articles:

				R. K. Buddington, K. K. Buddington, D.-F. Deng, G.-I. Hemre, and R. P. Wilson A High Retinol Dietary Intake Increases its Apical Absorption by the Proximal Small Intestine of Juvenile Sunshine Bass (Morone chrysopsxM. saxatilis) J. Nutr., September 1, 2002; 132(9): 2713 - 2716. [Abstract] [Full Text] [PDF]

				S. L. Weiss, E. A. Lee, and J. Diamond Evolutionary matches of enzyme and transporter capacities to dietary substrate loads in the intestinal brush border PNAS, March 3, 1998; 95(5): 2117 - 2121. [Abstract] [Full Text] [PDF]