The effect of pinealectomy and jejunal loop diversion on rat small bowel crypt cell kinetics.

Previously, it was found that diversion of an isolated loop of jejunum into the colon was associated with a significantly diminished crypt cell proliferation rate in the isolated loop, probably principally because of the diminished amount of nutrient available to the diverted mucosa. It has also been shown previously that removal of the pineal gland is associated with a considerable increase in the jejunal crypt cell mitotic rate. In the present investigation it was found that following pinealectomy, whilst the rise in crypt cell proliferation elsewhere in the rat small intestine was maintained at the expected level, the mitotic rate in the crypts of an isolated jejunal loop attached to the colon was also increased to a similar level, despite the fact that this isolated loop was in contact with a considerably diminished level of luminal nutrients. Thus, the expected hypoproliferative effects of jejunal isolation were overridden by the hyperproliferative effects of pinealectomy and the effects of pinealectomy appeared to be independent of the particular changes in luminal environment produced in this experiment. The significance of these findings is discussed in the light of the available literature.