Hypophysectomy-induced inhibition of augmented acetylcholine responses of the rat bowel following adrenalectomy and/or whole body irradiation.

Functional changes in the intestinal responsiveness to a fixed dose of acetylcholine were studied in muscle strips removed from young adult male rats previously exposed to whole body gamma radiation. In the irradiated rat the responsiveness to a fixed dose of acetylcholine was found to be augmented in the small intestine but not in the colon. Similar motor patterns for the small intestine were found when muscle strips from adrenalectomized rats were studied. Preradiation adrenalectomy further exaggerated the post-radiation sensitivity of the rat small intestine to acetylcholine. Hypophysectomy prior to either adrenalectomy and/or whole body radiation was associated with an absence of augmented small intestinal motor activity following administration of acetylcholine. The response of the large bowel to acetylcholine, however, was not modified by adrenalectomy and/or hypophysectomy. These observations suggest an endocrine component to the acute 3--5 day intestinal radiation syndrome.