A Paneth cell specific zinc-binding protein in the rat. Purification and immunohistochemical localization.

Background: Paneth cells are zinc-containing cells widely distributed in Lieberkühn's crypts of small intestine in many species, but their function has remained obscure. Our previous study showed that a single intravenous injection of diphenylthiocarbazone (dithizone), a zinc chelator, forms zinc-dithizonate complexes in the cytoplasm of Paneth cells to ensure rapid and selective killing of the cells.

Experimental Design: To verify the proteins that selectively deleted from intestinal mucosa after dithizone treatment, intestinal proteins from the rats with or without dithizone injection were compared in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. One such protein, a 90 kilodalton (kd) protein, was purified to homogeneity from normal rat intestine. A polyclonal antiserum was prepared by immunizing a rabbit with purified 90 kd protein to use in immunohistochemical study.

Results: Among several proteins deleted after dithizone injection, a 90 kd protein with an isoelectric point of 5.9 +/- 0.2, was purified to homogeneity from normal intestine by a combination of zinc affinity column and electroelution. Immunohistochemistry with rabbit anti-90 kd antiserum showed that the cytoplasmic granules in Paneth cells were stained. After dithizone administration, the 90 kd protein containing cells rapidly disappeared, but resumed as Paneth cells regenerated. Also positively stained with this antibody were a few mononuclear cells broadly distributed in the lamina propria of the digestive tract, but they were not affected by dithizone treatment.

Conclusions: A 90 kd zinc-binding protein was identified and purified from rat Paneth cells that was deleted in dithizone-treated rat intestine. We propose to designate it as a zinc-binding protein of Paneth cell.