Summary
From 148 BB-rats 76 animals (51.4%) developed hyperglycaemia within 55th to 178th day of life. Already before diagnosis of diabetes a great variety in pancreatic insulin
content and morphometrically determined relative β-cell volume density were visible.
Despite of this great heterogeneity two types in the course of β-cell destruction
could be observed.
Verified by individual retrospective analysis one part of the rats is characterized
by a more chronical course of diabetes development (pancreatic insulin content and
β-cell mass already more than 60 days before diagnosis of hyperglycaemia significantly
reduced, occurrence of insulitis) whereas other animals show an acute form of β-cell
destruction (still about 20 days before diagnosis of diabetes pancreatic insulin content
and relative β-cell volume density in a normal range). Besides a drastical reduction
of pancreatic insulin content at the time of diabetes diagnosis intense mono-nuclear
infiltrations in the islets of Langerhans causing their destruction are demonstrable.
As a result the residual β-cell volume is significantly reduced. Rats with a plasma
glucose higher than 13 mmol/l at diagnosis do not have any demonstrable β-cells and
an insulin content on the lowest detection limit of the method.
In animals with a more mild hyperglycaemia (plasma glucose 8.3 to 13 mmol/l) there
are rats with and the other ones without immunohistochemically detectable β-cells.
We conclude that prospective statements on the development of diabetes on the strength
of analysis of residual β-cells and pancreatic insulin content are not possible at
present. We suppose that there exist different processes of β-cell destruction which
have to be investigated in further studies including immunological parameters.
Key words
Pancreas - BB/OK Rats - Hyperglycaemia
