Effect of 1.25-dihydroxycholecalciferol administration on blood glucose and pancreatic islet morphology in mice.

1.25-dihydroxycholecalciferol (DHCC) administration to fed and starved mice had no effect on the blood-glucose concentration or the light-microscopic appearance of the endocrine or exocrine pancreas. Electron microscopy, however, disclosed changes which appeared early after the injection and were more marked in starved than in fed animals. The B-cells exhibited mitochondrial hypertrophy, studied both by qualitative and quantitative methods, invagination and vacuolation of mitochondrial membranes, increased occurrence of light secretory granules, multiple rough endoplasmic cisternae, multi-lamellar bodies, and a rather rich Ca2+-containing pyroantimonate precipitation mainly localized to nuclei and mitochondria. A tendency to mitochondrial hypertrophy was observed also in some D-cells. The A-cells were unaffected. The findings indicate that the endocrine pancreas (or at least the B-cells) is affected in some way, directly or indirectly, by DHCC.