Influence of 1,8-dihydroxyanthraquinone and loperamide on the paracellular permeability across colonic mucosa.

Administration of 1,8-dihydroxyanthraquinone (DHA) markedly increases the permeability of guinea-pig colonic mucosa. In 1 h 25% of the administered dose of 99mTc-EDTA complex leaks through the mucosa. Orally administered loperamide blocks the 99mTc-EDTA transfer after DHA administration. Loperamide injected in situ in the ligated colon segment shows the same blocking properties of the transfer rate of the complex. These findings suggest that the opposing action on fluid transport of the laxative DHA and the antidiarrhoeal loperamide could be due to these drugs affecting the permeability of the colonic mucosa. The minimal dose of loperamide, able to restore normal permeability, was as low as 0.01 mg kg-1.