Enterochromaffin Cells (EC) & Melatonin

The enterochromaffin cells (ECs) are the main producers of melatonin in the gastrointestinal (GI) tract. Initially identified in the Pineal gland, melatonin is now recognized as being synthesized throughout the GI tract, from the stomach to the colon. The Enterochromaffin Cells (EC) are known to produce several hundred times more melatonin than the amount produced by the pineal gland.
Raikhlin et al. 1975 Nature 255: 344-345
Pal et al. 2019a Melatonin Res 2: 61-81

Melatonin effects in the Intestine / Gastrointestinal Tract (Gut / GIT) are mediated by membrane receptors (MT1 and MT2). MT1 is expressed in the mitochondrial membrane while MT2 is also present in the nucleus
Bubenik 2008 J. Physiol. Pharmacol. 59: 33-51
Ahluwalia et al. 2018 Proc. Natl. Acad. Sci. USA 115: 1942-1943

The scientists demonstrated that both MT1 Receptors and Melatonin receptor 1B (MTNR1B) are present on the mitochondrial membrane of gastric endothelial cells
Rezzani et al. 2022 Int. J. Mol. Sci. 23: 3758

It is supposed that, in the gastric endothelial cells, the effects of melatonin via Mitochondria increases its protection in the Intestine / Gastrointestinal Tract (Gut / GIT)
Rezzani et al. 2022 Int. J. Mol. Sci. 23: 3758

In the stomach it has positive effects on the gastric mucosa against stress and ischemia and quickly induces ulcer healing
Sotak et al. 2017 Exp. Physiol. 102: 5-13
Ahluwalia et al. 2018 Proc. Natl. Acad. Sci. USA 115: 1942-1943