Fig. 4. Effects of chlorate and BzlGalNAc on post-translational maturation of pro-Muclin. (A) Pancreatic lobules were prepared from zymogen-granule-depleted mouse pancreas, pulse-labeled for 30 minutes in the presence of 30 mM NaCl, 30 mM chlorate, 2% DMSO or 32 mM BzlGalNAc. The samples were washed and chased in the continued presence of the chemicals for the indicated times. Equal amounts of tissue were run on SDS-PAGE (DNA equivalent to 3x10⁵ cells) and phosphorimaged. p80 was immunoprecipitated from equal aliquots (DNA equivalent to 2.7x10⁶ cells). The asterisk indicates the lower M_r form of Muclin produced in BzlGalNAc-treated cells. (B) Quantification of labeled pro-Muclin by phosphorimaging as a function of chase time expressed relative to the time zero incorporation of the appropriate control (NaCl and DMSO, respectively). (C) Quantification of labeled Muclin by phosphorimaging as a function of chase time expressed relative to the time zero incorporation into pro-Muclin of the appropriate control. (D) Quantification of p80 by phosphorimaging as a function of chase time expressed relative to the level at 4 hours of chase of the appropriate control. Data in B to D are from triplicate samples of a representative experiment and are means±s.d. (E) Lectin binding to pancreatic proteins. Pancreatic lobules were prepared from zymogen-granule-depleted mouse pancreas and incubated with 2% DMSO (vehicle) or 32 mM BzlGalNAc for 4 hours. Equal amounts of tissue were separated by SDS-PAGE followed by western blotting and probing with PNA (T antigen) and MAA (sialic acid).

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