Effect of N-formylated methionyl-phenylalanine (FMP) and methionyl-leucyl-phenylalanine (FMLP) on gut permeability. A model of local inflammatory process.

With the aim of elucidating inflammatory reactions in intestinal mucosa evoked by agents of microbial origin, the effect was assessed on intestinal permeability in the rat of two known chemoattractants for granulocytes and macrophages, N-formyl-methionyl-phenylalanine (FMP) and N-formyl-methionyl-leucyl-phenylalanine (FMLP). Fluoresceinated dextran (mol wt 3000 daltons) was used as a permeability marker. It was found that increasing concentrations of FMP enhanced the transmural passage up to a maximum at 2 X 10(-7)-2 X 10(-6)M. With FMLP the effect was greater than with FMP and measurable at 2 X 10(-9)-2 X 10(-8)M. The increased permeability was apparent 1-5 min after introduction of the peptides and prevailed during the 45-min measuring period. The bimodal response to the peptides is discussed in relation to different potential target-effector cells in the intestinal wall.