Recent advances on the importance of the serotonin transporter SERT in the rat intestine.

Serotonin (5-HT) is present in high concentration in enterochromaffin cells throughout the gastrointestinal tract, where it plays a very important role, being involved, e.g., in peristaltic and secretory reflexes in response to chemical or mechanical stimuli of the gut. Intestinal 5-HT is inactivated by metabolic degradation after cellular uptake mediated by the serotonin transporter SERT. This mini-review summarizes some recent data obtained by our group on the importance, regional distribution and cell membrane localization of SERT in the rat intestine. From our results, we conclude that SERT is located both at the apical and basolateral cell membranes of intestinal epithelial cells in the three intestinal regions studied: jejunum, ileum and colon. Moreover, we also conclude that inhibition of SERT causes an increase in transmural transport of 5-HT in these three intestinal segments, probably because it increases the extracellular concentration of 5-HT. Consequently, SERT inhibition will be able to cause an increase in the physiological responses of the tissue to this amine. The repercussions of this phenomenon are discussed.