TRANSPORT OF TETRACYCLINES ACROSS MOUSE ILEUM INVITRO - EFFECT OF CATIONS AND OTHER AGENTS

The intestinal transfer of different tetracyclines dissolved in Ca2+ and Mg2+-free Krebs bicarbonate buffer solution, pH 7.4 was studied using the everted mouse ileum. The rates of transfer of chlortetracycline and demethylchlortetracycline were less than those of tetracycline and oxytetracycline, the latter compounds being transferred at the same rate. Addition of Ca2+ and Mg2+ to the buffer greatly reduced the transfer of tetracycline; this inhibition could be antagonized by EDTA. The presence of Fe also inhibited the transfer of tetracycline. The inhibitory effect of these ions on tetracycline transfer seemed due to chelation of the drug. Glucosamine and acetylmethionine, but not acetyl glucosamine, diminished the intestinal transfer of tetracyclines. The former 2 agents did not influence the uptake of tissue fluids. Tetracycline was also transferred from the serous to the mucous coat in the non-everted intestinal sac of mice. The absorption of tetracyclines was probably not due solely to passive diffusion.