Background: Streptozotocin (STZ) is selectively toxic to the B cells in the pancreatic islets. It is well known that in the adult rat, STZ causes the death of B cells, and it eventually induces diabetes mellitus. The present study was conducted to detect what morphological changes could be induced in the fetal B cells following a direct injection of STZ into the fetus in utero during late pregnancy in the rat.
Methods: STZ (400 micrograms/g body weight) was injected into the fetus in utero at 10:00 on day 19 of gestation. Three, 6, 24, and 48 hr after injection, the changes in the B cells (anti-insulin serum positive cells) were examined immunohistochemically. The total volume of the B cells was measured. Electron microscopic observation was made as well.
Results: Six hr after STZ injection, some B cells were destroyed so that their granules were distorted and burst. Twenty-four hr after STZ injection, a large majority of the existing B cells were disintegrated, and a number of small isletlike clusters of immature cells appeared among the exocrine acini. The total volume of anti-insulin serum positive cells was strikingly decreased. At 48 hr after injection, however, the volume returned to a level that was comparable to that of their littermate controls.
Conclusions: The regeneration of the B cells may occur because of the high cell proliferative activity of undifferentiated cells following the destruction of the B cells caused by an injection of STZ.