Study of serotonin interactions with brush border membrane of rabbit jejunum enterocytes

Recent studies have demonstrated that serotonin (5-hydroxytryptamine, 5-HT) may interact with either specific receptors or with a specific transporter that takes up 5-HT in the gastrointestinal tract. The purpose of the prese nt work was to study the 5-HT interactions with brush border membrane from rabbit jejunum enterocytes. The results obtained showed that 5-HT did not s eem to be transported by any specific system of transport in brush border m embrane vesicles. Nevertheless, [H-3]5-HT seemed to bind specifically to th is membrane. The kinetic analysis indicated a saturable and dissociable spe cific binding with a dissociation constant K-D = 14 x 10(-9) M. The saturat ion studies with [H-3]5-HT indicated the presence of one specific site in t he brush border membrane. The results of displacement of [H-3]5-HT specific binding from the brush border membrane showed that both unlabelled 5-HT an d unlabelled GR113080 ([1-[(2-methyl sulphonyl) amino] ethyl-4-piperidinyl] methyl-1-methyl-1H-indole-3-carborylate), a specific competitive antagonis t of 5-HT4 receptors, inhibited the specific binding of [H-3]5-HT to this m embrane. (C) 2000 Elsevier Science B.V. All rights reserved.