DETECTION OF DEOXYRIBONUCLEASE-I ALONG THE SECRETORY PATHWAY IN PANETH CELLS OF HUMAN SMALL-INTESTINE

The expression and distribution of deoxyribonuclease I (DNase I) in hu man duodenum, jejunum and ileum were examined by DNase I activity assa y and the reverse transcriptase-polymerase chain reaction (RT-PCR), im munofluorescence, in situ hybridization, and immunocytochemical ultras tructural analyses. High levels of DNase I were detected in the cytopl asm of Paneth cells in human small intestine. A tissue homogenate frac tion rich in Paneth cells showed strong DNase I-specific enzymatic act ivity. Immunofluorescence analysis using several specific anti-human D Nase I antibodies showed very strong immunoreactivity in the cytoplasm of every Paneth cell. In situ hybridization demonstrated high levels of DNase I mRNA in Paneth cells. Immunogold electron microscopy reveal ed gold particles localized along the secretory pathway, with the exoc rine secretory granules mostly labeled. Our findings strongly suggest that Paneth cells synthesize and secrete DNase I into the intestinal l umen.