Ultrastructure of Paneth cells in germ-free rats, with special reference to the secretory granules and lysosomes.

Ultrastructure and acid phosphatase activity in Paneth cells, which are thought to play a role in regulation of the intestinal flora, were observed in control and germ-free rats (5 weeks of age, male). Examination of the germ-free rats revealed: secretory granules with coarse and a low-electron dense matrix in the duodenal, jejunal and ileal Paneth cells; numerous and larger lysosomes in ileal Paneth cells; and contact or fusion between the secretory granules and lysosomes in ileal Paneth cells. Acid phosphatase activities in Paneth cells were observed in the GERL of Novikoff (1964) and lysosomes in germ-free as well as control rats. None of the secretory granules showed any acid phosphatase activity. The fact that the lysosomes fused with the secretory granules suggests that the process of crinophagy occurred in the Paneth cells of germ-free rats.