THE LONG-TERM EFFECT OF PINEALECTOMY ON THE CRYPTS OF THE RAT GASTROINTESTINAL-TRACT

Previously it has been found that rat small bowel crypt cell hyperplas ia occurred several weeks after pinealectomy. To determine if this eff ect 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 stathmo kinetic technique. Although the hyperproliferative effect of pinealect omy 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 pos sible that regional differences in levels of gut neuropeptides or mela tonin are involved. The mechanism of the effect of pinealectomy on the crypts remains unexplained-in particular, why the effect is so prolon ged.