Proabsorptive action of gum arabic: regulation of nitric oxide metabolism in the basolateral potassium channel of the small intestine.
BACKGROUND
Gum arabic, a high-molecular-weight natural polysaccharide, has been shown to have proabsorptive properties in animal models of gastrointestinal disease that involve nitric oxide (NO). Gum arabic may indirectly regulate NO metabolism by creating an outward NO gradient, thus altering other intracellular NO-dependent mechanisms such as gating of the potassium (K+) channel. This hypothesis was further investigated using the K+ channel blocker, glybenclamide.


METHODS
Following intraperitoneal injection of 4.5 mg/kg glybenclamide or saline, the jejunum of anesthetized rats was perfused with a standard oral rehydration solution in the presence or absence of 2.5 g/L gum arabic, as well as 1 mmol/L l-arginine to enhance NO production. Sodium, net water, and glucose absorption and unidirectional water movement were determined.


RESULTS
Gum arabic showed regulatory capacity for NO-dependent metabolism by reducing net water absorption in the absence of arginine, and sodium absorption after arginine stimulation, in the absence of glybenclamide. Addition of gum arabic to oral rehydration solution, in glybenclamide pretreated animals, and in the absence of arginine, normalized sodium absorption, but was less effective in restoring net water transport. Injection of glybenclamide sharply decreased all absorption markers in arginine supplemented oral rehydration solution, which were at least partially restored by addition of gum arabic to the oral rehydration solution. In the presence of glybenclamide, the effects of arginine became antiabsorptive, as had those observed in preceding studies with high arginine concentration. Gum arabic partially or fully reversed alterations produced by perfused 1 mmol/L arginine.


CONCLUSIONS
Some of the effects of gum arabic on the small intestine are likely caused by its ability to remove NO as it diffuses into the lumen, thus reducing NO concentration in the enterocyte and indirectly affecting the absorptive/secretory response of the gut, which leads to normalization of absorptive function. These findings are consistent with the previously shown gum arabic-scavenging properties of NO and support a potential therapeutic role for this product.
Rehman
K
K
Division of Perinatal Medicine, Department of Pediatrics, North Shore-Long Island Jewish Health System, 300 Community Drive, Manhasset, NY 11030, U.S.A.
Wingertzahn
M A
MA
Harper
R G
RG
Wapnir
R A
RA
D000818:Animals; D001120:Arginine / Q000378:metabolism*; D001692:Biological Transport; D005440:Fluid Therapy; D005905:Glyburide / Q000494:pharmacology*; D006170:Gum Arabic / Q000494:pharmacology*; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007274:Injections, Intraperitoneal; D007408:Intestinal Absorption / Q000187:drug effects* / Q000502:physiology; D007421:Intestine, Small / Q000378:metabolism / Q000502:physiology*; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D010477:Perfusion; D015221:Potassium Channels / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D014867:Water / Q000378:metabolism
D007004:Hypoglycemic Agents; D015221:Potassium Channels; D014867:Water; D009569:Nitric Oxide; D006170:Gum Arabic; D001120:Arginine; D005905:Glyburide