Quantitative electron microscopic studies on rat ileal Paneth cells under various physiological and experimental conditions.

: The Paneth cells of the rat ileum were studied with quantitative electron microscopical methods. Estimations were made of the average volume of the cells and the nucleus, and the mean diameter and volume density of the secretory granules. Six groups of rats, each comprising 6-7 animals, were investigated: the rats in the first group were fasted controls, those in the second group non-fasted controls. In the third group the rats were given pilocarpine and in the fourth atropine. In the fifth group the rats were chemically sympathectomized, and the rats in the sixth group were subjected to partial removal of the small intestine. The secretory granules remained unchanged in all groups, except for the atropinized rats which contained significantly increased amounts, presumably indicating a low secretory rate. Moreover, the secretory granules were smaller in the rats treated with pilocarpine and in those operated on; this probably reflects a high secretory rate.