The effect of pinealectomy on the crypts of defunctioned rat colon

Previously it has been found that 6 months after pinealectomy hyperplasia occurred in the crypt cells of the rat small bowel and colon. It is also known that defunctioning a loop of colon, using a colostomy, results in crypt cell hypoplasia, emphasizing the prime importance of luminal factors in the control of crypt cell proliferation. To determine if the effects of pinealectomy on the colon could be modified by the absence of colonic luminal contents, the crypt cell kinetic effects of combined pinealectomy and defunctioning of a colonic loop by colostomy for 6 months were examined by using a stathmokinetic technique. It was found that the hypoproliferative effect of defunctioning a loop of colon was largely but not completely overridden by the hyperproliferative effect of pinealectomy. However, previously it has been found that in the rat small bowel, the hypoproliferative effects of defunctioning a loop were completely overridden by the effect of pinealectomy. This and other evidence suggests that the role of the pineal in the control of crypt cell proliferation in the colon may possibly be different from its role in the small bowel. There is other evidence of possible involvement of the pineal in carcinoma of the colon and it is possible that its role in the colon may be to prevent excessive mitotic activity, which is known to be present in the early stages of carcinoma. The Pineal gland may have a role in modulating the usual mechanisms of crypt cell mitotic control.