Polyploidy in the pancreas of the normal and diabetic mutant mouse.

The DNA content of endocrine and exocrine pancreatic nuclei of normal C57BL/KsJ and diabetic mutant C57BL/Ks-db/db mice was measured by Feulgen microdensitometry. The exocrine and endocrine pancreatic nuclei of the 4-week-old normal, 12-week-old normal, and 4-week-old (prehyperglycaemic) diabetic mutant mice contained diploid and tetraploid cells, while the 12-week-old (established hyperglycaemic) mutant contained diploid, tetraploid, and octaploid nuclei. The polyploidy in the endocrine pancreas of all these mice was confined to the B-cells, while the A-cells were always diploid.