Increased intracellular content of enteroglucagon in proximal colon is related to intestinal adaptation to germ-free status

Changes in the frequency of endocrine cells are evidence of intestinal adap tation to germ-free (GF) status. Not only the distribution of these cells a long the intestine, but also the differences in intracellular content of th ese regulatory peptides may be explored to explain functional and structura l aspects of GF intestinal adaptation. Focusing on the endocrine L-cells, w e analyzed the intracellular content of enteroglucagon (EG) and peptide YY (PYY) throughout the intestine of the 14 GF and 14 conventional (CV) mice b y using immunohistochemistry and the supra-optimal dilution technique. The percentage of EG-immunoreactive cells, but not of PYY-immunoreactive cells stained at supra-optimal dilution was significantly higher in the proximal colon of GF mice than in the CV counterparts (P < 0.05). Since the content of co-stored PYY did not differ between GF and CV mice, the higher content of EG was compatible with a selective cellular response. Moreover, in the c ecum of GF mice, the density of EG-immunoreactive cells was significantly h igher than that of PYY-immunoreactive cells (P < 0.05). These results are c onsistent with preferential production of EG by L-cells at the expense of P YY in the proximal colon and in the enlarged cecum of GF mice. In addition, they may reflect the dynamics of the GF intestinal epithelium and/or be co rrelated with the higher serum levels of these peptides. The role of endocr ine cells needs to be better studied in human and other experimental adapta tive conditions in order to elucidate the regulatory mechanisms of intestin al functions.