However, the amount of melatonin produced in the GI tract by enterochromaffin cells
is 400 times greater than that produced by the pineal gland.
It is thought that CT stimulates enterochromaffin cells
to release serotonin, and that serotonin then promotes the release of the secretagogue vasointestinal peptide from intestinal neural networks (40).
"LX1031 acts locally on enterochromaffin cells
in the GI tract to inhibit tryptophan hydroxylase, the rate-limiting enzyme in the synthesis of serotonin," explained Dr.
Serotonin (5'-hydroxy tryptamine; 5-HT) is a bioamine, which is synthesized from L-tryptophan mainly in enterochromaffin cells
of the gastrointestinal tract and central nervous system.
Pulmonary arterial hypertension has been described in type Ia, possibly due to an abnormally excessive production of vasoconstrictor amines like serotonin that is synthesized from the intestinal enterochromaffin cells
. Hence, this becomes a plausible means in studying patients suspected of having type Ia glycogenosis; however, we should not discard the effect caused by the endothelial damage from the presence of metabolic alterations like hyperlipemia (3,4).
It is secreted by the enterochromaffin cells
of the microvilli and it promotes peristalsis in the GIT.
In midgut carcinoids derived from enterochromaffin cells
located in the small intestines, cecal region, and ascending colon (10), serotonin (5-hydroxytryptamine) is the major metabolic product.
In GVHD there is a selective sparing of enterochromaffin cells
in colon, and single or small clusters of endocrine cells can be seen in lamina propria (9) (Figure 2, C).