Endotoxemia in mice stimulates production of complement C3 and serum amyloid A in mucosa of small intestine.

We examined the effect of endotoxemia in mice on protein and mRNA levels for the acute phase proteins complement C3 and serum amyloid A (SAA) in jejunal mucosa. Endotoxemia was induced in mice by the subcutaneous injection of 250 microg lipopolysaccharide per mouse. Control mice were injected with saline. C3 and SAA were measured by ELISA. Messenger RNA levels were determined by Northern blot analysis or competitive PCR. Immunohistochemistry was performed to determine in which cell type(s) C3 and SAA were present. Mucosal C3 and SAA protein and mRNA levels were increased in endotoxemic mice. Immunohistochemistry showed that C3 was present in both enterocytes and cells of the lamina propria, whereas SAA was seen mainly in lamina propria cells. Results suggest that endotoxemia stimulates production of C3 and SAA in small intestinal mucosa. The response may be regulated at the transcriptional level and probably reflects increased synthesis of the acute phase proteins in both enterocytes and cells of the lamina propria.