Comparative study of erythromycin, troleandomycin and tylosin on the rabbit intestine.

The macrolide antimicrobial agents, erythromycin, troleandomycin and tylosin were tested for their effect on isolated whole segments of the rabbit duodenum, jejunum, ileum and ascending colon, as well as on strips of the circular and longitudinal smooth muscle of the ascending colon. The 14-membered macrolides erythromycin and troleandomycin were found to possess a concentration-dependent contractile effect on the intestinal smooth muscle. The order of potency was: erythromycin > troleandomycin. The 16-membered macrolide tylosin was found to have a much weaker potency than erythromycin and troleandomycin. In addition, the circular smooth muscle of the ascending colon was found to be more sensitive to the compounds tested than the longitudinal smooth muscle.