5-HT metabolism in the intestinal wall of the rat—I. The mucosa

Serotonin (5-HT) metabolism was studied on isolated mucosa of the rat caecum in order to determine its characteristics in enterochromaffin cells. High levels of 5-HT were found in these cells and weak catabolic processes were demonstrated. Enterochromaffin cells of the mucosa are able to synthesize ( 3H)5-HT from ( 3H)tryptophan in vitro indicating that these cells might contain tryptophan hydroxylase. In addition, a high affinity uptake of exogenous ( 3H)5-HT is demonstrated. These results show that enterochromaffin cells of the mucosa present similar biochemical properties compared to those described for serotoninergic neurons of the central nervous system.