Alloxan-induced diabetes in the mouse: time course of pancreatic B-cell destruction as reflected in an increased islet vascular permeability.

The extent to which injections of the pancreatic B-cytotoxin alloxan in C57BL/Ks mice induced an increase in islet vascular permeability, and the time course of this increase, were studied. The vascular permeability was monitored by administration of the dye Monastral blue B, which is entrapped in leaky blood vessels with intact basement membranes. The islets were visualized by a freeze-thawing technique which allows identification of stained islets. Not until four hours after the alloxan injections was there an increase in islet uptake of Monastral blue B when compared with saline-treated control animals. Thereafter the islet staining increased further. The process was accompanied by gradual development of hyperglycaemia and a reduction of number of the islets identified in the pancreatic preparations. It is concluded that alloxan causes an increase in islet vascular permeability, which appears to become manifest at a later stage than the cytotoxic B-cell degeneration.