The protection of insulin against proteolytic processes after rectal application to normoglycemic rabbits

In order to improve the bioavailability of insulin after rectal application to rabbits, the influence of surface-active amino acid-fatty acid condensate on absorption and, the effects of a protease inhibitor (aprotinine), of a disinfectant (methyl-hydroxybenzoate) and of chemotherapeutics (chloramphenicol, ambazone and metronidazole) were investigated. Only the application of methylhydroxybenzoate, ambazone and of metronidazole, which inhibit the anaerobic bacterial flora, improved bioavailability significantly. The examinations show that the proteolytic activity of the anaerobic bacterial flora causes the loss of the biological activity of peptides in the rectum.