title: Transmural fluxes of 5-hydroxytryptamine in guinea pig ileum.
abstract: Transmural movement of 5-hydroxytryptamine (5-HT) was studied in guinea pig small intestine in vitro in order to test the hypothesis that there is mucosal 5-HT barrier in this species. Segments of guinea pig ileum were mounted as flat sheets in flux chambers or were everted and perfused. Mucosal-to-serosal (Jm leads to s) and serosal-to-mucosal (Js leads to m) fluxes of 5-HT were measured in the absence of 5-HT gradients and under open- or short-circuited conditions. The results indicated that substantial transmural movement of 5-HT occurred in these preparations. Both Jm leads to s and Js leads to m were linear functions of the 5-HT concentration over a range of 1-30 microM and were not significantly different in the two directions. Addition of 2,4-dinitrophenol to both sides of the tissue reduced short-circuit current to zero and increased both tissue conductance and unidirectional 5-HT fluxes. These results suggested that the 5-HT fluxes across the guinea pig ileum occurred by passive mechanisms. Fluxes of 5-HT across preparations with the muscularis externa removed were not significantly different from fluxes across intact preparations. Mucosal-to-serosal 5-HT fluxes in everted perfused sacs were comparable with fluxes in the flat-sheet preparations. The data are not consistent with the hypothesis of a "tissue barrier" that functions to prevent 5-HT from reaching serotonergic receptors on enteric ganglion cells or enteroendocrine cells.
mesh_terms: D019297:2,4-Dinitrophenol; D000818:Animals; D004140:Dinitrophenols / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects / Q000294:innervation / Q000378:metabolism*; D007408:Intestinal Absorption / Q000187:drug effects; D007413:Intestinal Mucosa / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D009197:Myenteric Plexus / Q000502:physiology; D010293:Pargyline / Q000494:pharmacology; D012701:Serotonin / Q000378:metabolism*
chemical_list: D004140:Dinitrophenols; D012701:Serotonin; D010293:Pargyline; D019297:2,4-Dinitrophenol