AJP - Gastrointestinal and Liver Physiology, Vol 259, Issue 2 290-G299, Copyright © 1990 by American Physiological Society

ARTICLES

Paracellular intestinal absorption of glucose, creatinine, and mannitol in normal animals: relation to body size

J. R. Pappenheimer
Department of Biology, Harvard University, Bedford, Massachusetts 01730.

Mice, rats, or rabbits were provided with a liquid diet of 10-12% glucose (Glc), 0.5-1% creatinine, 1-2% mannitol, and mannitol labeled with 3H on a terminal carbon. Average rates of ingestion of Glc were greater than maximum rates of active, carrier-mediated Glc transport reported for the intestines of these species. The discrepancy was small in mice but increased exponentially with body weight (BW). Ingestion-absorption of Glc increased exponentially with the 0.73 power of BW as expected from metabolic rate, whereas active transport, estimated from the literature, varied exponentially with the 0.50 power of BW. It is estimated that in humans the ingestion-absorption rate of Glc may be 10-20 times greater than active transport. In the presence of Glc, 50-65% of the ingested creatinine was recovered in urine compared with 75-85% recovered after intraperitoneal or subcutaneous injections. The amount of creatinine recovered in urine depended on the amount of ingested Glc, as predicted from the effects of Glc on width and permeability of absorptive cell junctions. Eighty percent or more of the 3H label on mannitol was recovered in urine or other body fluids, although most of the [3H]mannitol was oxidized to [3H]water after being absorbed intact from the intestine. It is concluded that in the presence of Glc, creatinine and mannitol (together with Glc, amino acids, and other small nutrients) are absorbed passively by solvent drag between absorptive cells, as found previously in anesthetized rats (J. R. Pappenheimer and K. Z. Reiss. J. Membr. Biol. 100: 123-136, 1987). The ratio of solvent drag to carrier-mediated transport increases exponentially with BW and may account for the capacity of human intestines to absorb large amounts of Glc during prolonged exercise, Glc tolerance tests, or oral Glc-saline therapy for dehydration.

This article has been cited by other articles:

				Y. Kimura, J. R. Turner, D. A. Braasch, and R. K. Buddington Lumenal adenosine and AMP rapidly increase glucose transport by intact small intestine Am J Physiol Gastrointest Liver Physiol, December 1, 2005; 289(6): G1007 - G1014. [Abstract] [Full Text] [PDF]

				T. J. McWhorter, C. M. del Rio, and B. Pinshow Modulation of ingested water absorption by Palestine sunbirds: evidence for adaptive regulation J. Exp. Biol., February 15, 2003; 206(4): 659 - 666. [Abstract] [Full Text] [PDF]

				S. Desmeules, P. R. de Cotret, and P. Isenring A woman with hyponatraemia, acidosis, aneuria and terminal ileostomy Nephrol. Dial. Transplant., July 1, 2002; 17(7): 1342 - 1347. [Full Text] [PDF]

				J. P. Cant, P. H. Luimes, T. C. Wright, and B. W. McBride Modeling intermittent digesta flow to calculate glucose uptake capacity of the bovine small intestine Am J Physiol Gastrointest Liver Physiol, June 1, 1999; 276(6): G1442 - G1451. [Abstract] [Full Text] [PDF]

				B Scholtka, F Stumpel, and K Jungermann Acute increase, stimulated by prostaglandin E2, in glucose absorption via the sodium dependent glucose transporter-1 in rat intestine Gut, April 1, 1999; 44(4): 490 - 496. [Abstract] [Full Text] [PDF]

				M R Uhing Effect of sodium ion coupled nutrient transport on intestinal permeability in chronically catheterised rats Gut, July 1, 1998; 43(1): 22 - 28. [Abstract] [Full Text] [PDF]

				E. Weber and H. J. Ehrlein Reserve capacities of the small intestine for absorption of energy Am J Physiol Regulatory Integrative Comp Physiol, July 1, 1998; 275(1): R300 - R307. [Abstract] [Full Text] [PDF]

				J. R. Pappenheimer, M. L. Karnovsky, and J. E. Maggio Absorption and Excretion of Undegradable Peptides: Role of Lipid Solubility and Net Charge J. Pharmacol. Exp. Ther., January 1, 1997; 280(1): 292 - 300. [Abstract] [Full Text]