Effect of erythromycin on L-threonine transport in rabbit jejunum in vitro

Effects of Acute and Chronic Exposure to Residual Level Erythromycin on Human Intestinal Epithelium Cell Permeability and Cytotoxicity

Residual concentrations of erythromycin in food could result in gastrointestinal tract exposure that potentially poses a health-hazard to the consumer, affecting intestinal epithelial permeability, barrier function, microbiota composition, and antimicrobial resistance. We investigated the effects of erythromycin after acute (48 h single treatment with 0.03 μg/mL to 300 μg/mL) or chronic (repeated treatment with 0.3 µg/mL and 300 µg/mL erythromycin for five days) exposures on the permeability of human colonic epithelial cells, a model that mimics a susceptible intestinal surface devoid of commensal microbiota. Transepithelial electrical resistance (TER) measurements indicated that erythromycin above 0.3 µg/mL may compromise the epithelial barrier. Acute exposure increased cytotoxicity, while chronic exposure decreased the cytotoxicity. Quantitative PCR analysis revealed that only ICAM1 (intercellular adhesion molecule 1) was up-regulated during 0.3 μg/mL acute-exposure, while ICAM1, JAM3 (junctional adhesion molecule 3), and ITGA8 (integrin alpha 8), were over-expressed in the 300 μg/mL acute treatment group. However, during chronic exposure, no change in the mRNA expression was observed at 0.3 μg/mL, and only ICAM2 was significantly up-regulated after 300 μg/mL. ICAM1 and ICAM2 are known to be involved in the formation of extracellular matrices. These gene expression changes may be related to the immunoregulatory activity of erythromycin, or a compensatory mechanism of the epithelial cells to overcome the distress caused by erythromycin due to increased permeability.

Study of the action of intramuscularly administered erythromycin on the L-threonine transport and the digestive enzymatic activity in rabbit jejunum

Erythromycin has been shown to inhibit the intestinal transport of L-threonine and D-galactose in strips of mucosal jejunum when it was directly added to the incubation medium. Nevertheless, the effect of erythromycin administered therapeutically by intramuscular injection on both the intestinal absorption of nutrients and the intestinal digestive activity, remains unknown. The results obtained show that, firstly, the intestinal absorption of L-threonine is inhibited in animals treated with erythromycin. The kinetic study shows that the effect seems to be mainly due to an alteration of the affinity apparent constant (Kt) of the Na(+)-dependent system of transport located in the mucosal border. However, the Na(+)-dependent L-threonine transport in BBMV was not altered by the treatment with erythromycin. The (Na(+)-K+) ATPase activity in BLMV from treated jejunum was 40% of the activity in control BLMV. Secondly, the treatment with erythromycin did not modify the digestive enzymatic activity of sucrase and aminopeptidase N.

Effect of motilin on the L-leucine transport in rabbit jejunum

Motilin is a gastrointestinal peptide that stimulates the gastrointestinal motility in several species. The aim of the present work has been to determine the effect of motilin on the L-leucine absorption in rabbit jejunum. The results show that motilin inhibits the L-leucine Na(+)-dependent system of transport located in the mucosal border mainly by diminishing the apparent Vmax. Motilin did not directly affect the Na(+)-dependent system of transport, but it seems to act across the protein kinase C (PKC). These results suggest that motilin may act as a regulatory hormone of the intestinal absorption of nutrients.

Macrolides in roles beyond antibiotic therapy

Erythromycin and other macrolides with a closely related structure are widely used antibiotics. Side-effects related to administration of such drugs are mostly gastrointestinal. The direct effect of erythromycin on gastrointestinal motility was studied; it was found to have a stimulatory effect proximally, on stomach and duodenal motility, with an apparent distal inhibition. Gastric emptying was accelerated by erythromycin via an antroduodenal coordination mechanism, an effect that has proved to be beneficial in surgical and medical conditions in which gastroparesis is a problem. Erythromycin is now used experimentally and clinically; it has been found to accelerate gastric as well as gallbladder emptying and to have an effect on the oesophagus. Analogues of erythromycin have been developed that have potent gastrointestinal activity but little or no antibacterial potential. Macrolides modulate the antibacterial action of neutrophils, with some action on the oxidative burst. Finally, two new macrolide immunosuppressants have been developed that compare favourably with traditional drugs.