Peptides as Promotors of Paracellular Permeability: A Novel Role For Tachykinins?

As ions move across epithelial sheets, they can do so either through the cells (transcellular) or between them (paracellular). Such transfers result in the development of trans-epithelial potential differences (P.D.’s) that are readily observed when these epithelia are set up in Ussing chambers, in vitro [1]. Alterations in the P.D.’s thus developed can be conveniently analyzed in terms of the modulation of either one or both of the above routes of permeation. Although a number of transmitters and hormones have been shown to modulate trans cellular ion movements, relatively few modulators of paracellular pathways have been described; these include, among others, cyclic AMP, Ca 2+, carbachol, pancreozymins, and prostaglandins [2–5]. Luminal addition of several peptides [6–9] produce marked effects on the isolated canine tracheal epithelium. Our studies reported here suggest that these pep tides (SP, tachykinins, bradykinin) could rapidly alter the conductance of the paracellular pathways.