Spontaneous diabetes mellitus in the New Zealand white rabbit: preliminary morphologic characterization.

Electron microscopic studies on a closed colony of rabbits with an 18.5 per cent incidence of spontaneous onset insulin-dependent diabetes mellitus revealed that the beta-cells of the islets of Langerhans of the diabetic animals were hypergranulated. This finding contrasts with most other animal models of spontaneous diabetes mellitus which show degranulation of the beta-cells. There was no evidence of hyperplasia, insulitis, amyloid, or fibrosis of the islets by either light or electron microscopy. Correlation of our morphologic findings with physiologic data suggests a defect in insulin secretion. Rabbits with normal glucose metabolism showed a normal degree of granulation of their beta-cells. The alpha and delta cells were within normal limits in all animals. No other abnormalities associated with diabetes in humans or other animals were noted except for minimal fusion of the glomerular epithelial foot processes and mineralization of the proximal tubules and Bowman's capsules.