Defective cytoplasmic granule formation.II. Differences in patterns of radiolabeling of secretory granules in beige versus normal mouse pancreatic acinar cells after [3H]glycine administration in vivo.

We investigated the development of secretory granules in the pancreatic acinar cells of normal (C57BL/6J +/+) and beige (C57BL/6J Lystbg/Lystbg) mice by analyzing the distribution of 3H label in pancreatic acinar cells after a pulse of [3H]glycine administered in vivo. The results provide quantitative confirmation of the hypothesis that the maturation of condensing vacuoles/immature granules to mature granules in pancreatic acinar cells is associated with a significant volume reduction. Beige mice differ from control mice by exhibiting a more rapid distribution of 3H label from the rough endoplasmic reticulum-rich cytoplasm to the secretory granules and a slightly faster rate of maturation of 3H-labeled granules. Beige mouse pancreatic acinar cells also exhibited, as early as 1 h after pulsing with [3H]glycine, a much higher proportion of 3H-labeled secretory granules than did the cells of control mice. These findings identify additional abnormalities in secretory granule formation in pancreatic acinar cells which are related to the beige (Lystbg) mutation and provide support for the hypothesis that beige mice exhibit an abnormal pattern of granule-granule fusion.