The long‐term effect of pinealectomy on the crypts of the rat gastrointestinal tract

Abstract

Previously it has been found that rat small bowel crypt cell hyperplasia occurred several weeks after pinealectomy. To determine if this effect was longer-lasting (because of the possible role of the pineal in bowel malignancy) the crypt cell proliferation rate was determined in rat small bowel and colon 6 months after pinealectomy, using a stathmokinetic technique. Although the hyperproliferative effect of pinealectomy was well maintained in the small bowel crypts after 6 months, the hyperproliferative effect in the colonic crypts was much less marked. There is no obvious explanation for these findings, although it is possible that regional differences in levels of gut neuropeptides or melatonin are involved. The mechanism of the effect of pinealectomy on the crypts remains unexplained--in particular, why the effect is so prolonged.

The Effect of Exogenous Melatonin on Experimental Colonic Anastomosis

“…The effect of pinealectomy on wound healing of the gastrointestinal tract was, however, to increase epithelial proliferation (6,7). Contrary to these findings, another study from our institution concluded that pinealectomy has no effect on the healing of colonic anastomoses (8).…”

“…Due to the multifactorial nature of colonic dehiscence, efforts have been devoted to investigating the effects of various interventions and pharmacological agents on colonic anastomosis. Even though it is known that pinealectomy and melatonin affect gastro-intestinal healing (6)(7)(8)(9), there is no study in the English literature dealing with the effect of exogenous melatonin on the mechanical strength of gastro-intestinal anastomosis.…”

Molecular mechanisms of the pro-apoptotic actions of melatonin in cancer: a review

“…Melatonin is synthesized in the gastrointestinal tract and its levels are unrelated to indole synthesis in the pineal gland, given that pinealectomy in rats had no influence on melatonin levels in the gastrointestinal tract [78] although small bowel crypt cell hyperplasia occurred after removal of pineal gland [79], leading to the appearance of pre-neoplastic features [80]. Melatonin plays a role in the physiological control of proliferation of the crypts of rat colon [81] and prevents the development of dimethyl-hydrazine-induced gastrointestinal cancers [82].…”

Localization, Physiological Significance and Possible Clinical Implication of Gastrointestinal Melatonin

“…Pinealectomy increased the mitotic index in the rat intestinal crypts [129]. Callaghan [130,131] reported that the hyperproliferative effect of P x may be mediated by the vagal and sympathetic innervation of the gut and that it can last as long as 6 months. In another study, melatonin was found to reduce the proliferation of jejunal epithelium in mice [132], but melatonin given alone did not influence mitotic activities in the gastric mucosal epithelium of rats [133].…”