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. 1994 Mar 1;91(5):1942–1945. doi: 10.1073/pnas.91.5.1942

Intestinal absorption and excretion of octapeptides composed of D amino acids.

J R Pappenheimer 1, C E Dahl 1, M L Karnovsky 1, J E Maggio 1
PMCID: PMC43280  PMID: 8127911

Abstract

Octapeptides synthesized from D amino acids were absorbed from the intestine and excreted in urine of normal rats drinking 5% glucose/1% creatinine containing the 125I-labeled peptides at 0.1-25 mg/dl. The rats ingested fluid at the rate of about 20 ml/hr and produced urine at 15 ml/hr for several hours during the nocturnal feeding period. Sixty-one +/- 4% of the ingested creatinine and 50 +/- 3% of a lipid-insoluble D octapeptide (EASASYSA, 784 Da) were excreted intact in the urine. The steady-state molar rate of absorption-excretion of creatinine equaled or exceeded the maximum rate of carrier-mediated intestinal transport of glucose, suggesting that both the creatinine and the D octapeptide were transported paracellularly by solvent drag through absorptive cell junctions that were dilated by the glucose. More than 70% of the ingested glucose was also absorbed paracellularly. The results demonstrate that intact oligopeptides can be absorbed efficiently from the intestine when they are not hydrolyzed by membrane-bound peptidases of the brush border. The results also provide support for recent theories proposing that coupling of membrane digestion with paracellular solvent drag accounts for a major fraction of normal intestinal absorption of nutrients.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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