Beta cell selectivity of streptozotocin
Streptozotocin is a nitrosourea analogue in which the N-methyl-N-nitrosourea (MNU) moiety is linked to the carbon-2 of a hexose. The toxic action of streptozotocin and chemically related alkylating compounds requires their uptake into the cells. Nitrosoureas are usually lipophilic and tissue uptake through the plasma membrane is rapid; however, as a result of the hexose substitution, streptozotocin is less lipophilic. Streptozotocin is selectively accumulated in pancreatic beta cells via the low-affinity GLUT2 glucose transporter in the plasma membrane. Thus, insulin-producing cells that do not express this glucose transporter are resistant to streptozotocin. This observation also explains the greater toxicity of streptozotocin compared with N-methyl-N-nitrosourea in cells that express GLUT2, even though both substances alkylate DNA to a similar extent. The importance of the GLUT2 glucose transporter in this process is also shown by the observation that streptozotocin damages other organs expressing this transporter, particularly kidney and liver.