Prospective Investigations of Long-term Normoglycaemic BB/OK-rats: Serial Determination of Glucose Tolerance, Insulitis, B-cell Volume Density and Pancreatic Insulin Content

Summary

Pancreatic tissue was obtained by repeated surgical biopsies from BB/OK rats (n = 62), which maintained normoglycaemia up to 250 days. The tissue was used to determine pan creatic insulin content, islet volume density, pancreatic B-cell volume density and the presence of mononuclear cell infiltrations within and around pancreatic islets (insulitis). The BB/OK rats were also characterized by determination of glucose tolerance.

In 50 d old BB/OK rats lymphatic infiltration of pancreatic islets are rare. The mean value of relative B-cell volume density amounted to 0.71 + 0.05% and the pancreatic insulin content was 21.31 + 1.29 pmol/mg wet weight. 70 d old BB/OK rats are characterized by an identical relative B-cell volume density and pancreatic insulin content, although in 70% of the animals an invasion of immunocytes could be observed. At an age of 90 and 120 d the BB/OK rats were characterized by an increased number of islets having insulitis accompanied by a decrease of pancreatic insulin content and B-cell volume density. The individual evaluation of the investigated BB/OK rats revealed in each animal the presence of insulitis accompanied by a decreased B-cell volume density and a diminished pancreatic insulin content. Animals older than 120 d do reenhance the pancreatic insulin content and B-cell volume density attended by an impairment of glucose tolerance. The results suggest that all BB/OK rats are characterized by a spontaneous pancreatic B-cell destruction, which was arrested and/or interrupted in the animals maintaining normoglycaemia up to 250 d.

Key words

Normoglycaemic BB/OK rats - Insulitis - B-cell volume density - Pancreatic insulin content