The Effects of Enterotoxins and Short-Chain Fatty Acids on Water and Electrolyte Fluxes in Heal and Colonic Loops in vivo in the Rat

Abstract

The effect of cholera toxin (CT) and Escherichia coli heat-stable enterotoxin (ST) on the ileum and colon was examined in vivo in the rat in an attempt to clarify the effects of enterotoxins on colonic mucosa and to determine if these effects were influenced by short-chain fatty acids (SCFA). Both CT and ST induced similar changes in water and electrolyte fluxes, and the magnitude of these changes in loops of colon was similar to that observed in loops of ileum. The addition of luminal SCFA, acetate, propionate and butyrate did not influence the effect of either toxin in loops of ileum. However, in loops of colon exposed to CT, luminal butyrate (40 mM) largely reversed the effect of CT by converting net water secretion (mean ± SE, -363 ± 154 nl•cm^-2•min^-1) to net water absorption (470 ± 194 nl·cm^-2·min^-1) and by significantly reducing the net secretion of sodium ions. In loops of colon exposed to ST, similar effects were observed although net water secretion (-784 ± 114 nl•cm^-2•min^-1) was only partially reversed by butyrate (-318 ± 102 nl•cm^-2•min^-1). In contrast to butyrate, acetate and propionate did not influence changes in colonic fluxes of water and sodium induced by enterotoxins. Oxidation of butyrate and glucose was observed to be depressed in colonocytes pre-exposed to CT but not to ST. In this model, colonic secretion induced by enterotoxins is similar to that observed in the ileum but differs from ileal secretion in its modulation by luminal butyrate.

Transport of butyryl-l-carnitine, a potential prodrug, via the carnitine transporter OCTN2 and the amino acid transporter ATB0,+

“…The homozygous jvs mouse develops villous structure atrophy, inflammation, spontaneous perforations, and pus formation in the peritoneal cavity (49a). Furthermore, several anecdotal reports have shown a beneficial effect of carnitine and butyrate enemas in some cases of distal IBD (4,16,18,39). Short-chain fatty acids not only exert a nutritional effect on the gut but also are protective for enterocytes.…”

A zinc-sensing receptor triggers the release of intracellular Ca 2+ and regulates ion transport

“…In addition, zinc ions in physiological concentrations decrease the membrane potential in oxyntic cells, thereby reducing the transport of K ϩ , Cl Ϫ , and NO 2 (4,(48)(49)(50)(51). The Na ϩ ͞H ϩ exchanger plays a central role in vectorial Na ϩ transport and pH homeostasis in the colon (52)(53)(54). Activation by Ca i 2ϩ has been demonstrated for the Na ϩ ͞H ϩ exchanger in several cell lines (55)(56)(57).…”

Fermentation in the large intestine of single-stomached animals and its relationship to animal health

“…Until recently, the principal physiological functions of the large intestine have been considered to be the conservation of water and electrolytes (Dobbins & Binder, 1981;Ramakrishna et al 1990), provision of a controllable route for the excretion of waste products of metabolism and toxic substances, and safe containment of the micro-organisms present (Cummings, 1983). However, it is now realized that one of the principal functions must include the salvage of energy and nutrients through its symbiotic relationship with the GIT microflora.…”