Intestinal permeability enhancement: efficacy, acute local toxicity, and reversibility

The absorption of the polar drug phenol red was assessed in a rat intestinal perfusion model, in the presence of a variety of potential intestinal permeability enhancers. Both the absorption rate constant KA and the plasma phenol red concentration were measured. Perfusates were also assayed for the presence of lactate dehydrogenase (LDH) and lipid phosphate, as biochemical markers of intestinal wall damage. Histological evaluation of surfactant-perfused intestines was also carried out. The potential permeability enhancers studied were the surfactants sodium dodecyl sulfate (SDS), sodium taurocholate (TC), sodium taurodeoxycholate (TDC), polysorbate-80 (PS-80), and nonylphenoxypolyoxyethylene (NP-POE) with an average polar group size of 10.5 POE units. Among these, SDS and NP-POE-10.5 were the most potent permeability enhancers. The bile salt TDC was a more effective enhancer than the more polar TC. The polar non-ionic surfactant PS-80 was an ineffective enhancer. Phenol red KA and plasma level were generally correlated with biochemical and histological measures of intestinal damage. These observations indicate that permeability enhancement and local damage are closely related sequelae of the interaction of surfactants with the intestinal wall, and suggest that local wall damage may be involved in the mechanism of permeability enhancement. The reversibility of permeability enhancement and acute local damage was assessed for the surfactants TDC and NP-POE-10.5. Enhancement of phenol red permeability was reversed within 1-2 hr of the cessation of enhancer treatment. Biochemical markers of local damage also fell to control values within 1-2 hr of removal of enhancer from the perfusate. Histological evaluation of perfused intestines revealed that morphological damage was reversed within 3 hr. These results demonstrate that surfactant-induced acute intestinal wall damage is rapidly repaired.