Relative importance of transport and alkylation for pancreatic beta-cell toxicity of streptozotocin.
OBJECTIVE
The role of selective uptake and alkylation in the diabetogenic action of streptozotocin was investigated in bioengineered RINm5F insulin-producing cells, with different expression levels of the glucose transporter GLUT2, by comparing the toxicity of streptozotocin with that of four chemically related alkylating compounds, N-methyl-N-nitrosourea (MNU), N-ethyl-N nitrosourea (ENU), methyl methanesulphonate (MMS) and ethyl methanesulphonate (EMS).


METHODS
GLUT2 expressing RINm5F cells were generated through stable transfection of the rat glucose transporter GLUT2 cDNA under the control of the cytomegalovirus promoter in the pcDNA3 vector. Viability of the cells was determined using a microtitre plate-based 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay.


RESULTS
Cells expressing the glucose transporter GLUT2 were much more susceptible to streptozotocin toxicity than control cells due to the uptake of streptozotocin by this specific glucose transporter. In contrast, the GLUT2 expression had no effect upon the toxicity of MNU, ENU, MMS or EMS. Although the latter substances are, like streptozotocin, cytotoxic through their ability to cause DNA alkylation, they are not diabetogenic because they are not taken up through the glucose transporter GLUT2.


CONCLUSIONS
Our results are consistent with the central importance of selective uptake and alkylating activity in the mechanism of streptozotocin diabetogenicity. Alkylation of DNA leads to necrosis of pancreatic beta cells and thus to a state of insulin-dependent diabetes mellitus, well-known as streptozotocin diabetes in experimental diabetes research.
Elsner
M
M
Institute of Clinical Biochemistry, Hannover Medical School, Hannover, Germany.
Guldbakke
B
B
Tiedge
M
M
Munday
R
R
Lenzen
S
S
D019325:3-O-Methylglucose / Q000493:pharmacokinetics; D000477:Alkylating Agents / Q000493:pharmacokinetics / Q000633:toxicity*; D000478:Alkylation; D000818:Animals; D001692:Biological Transport; D001711:Biotransformation; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D005020:Ethyl Methanesulfonate / Q000633:toxicity; D005038:Ethylnitrosourea / Q000633:toxicity; D051273:Glucose Transporter Type 2; D007515:Islets of Langerhans / Q000187:drug effects* / Q000473:pathology; D007700:Kinetics; D008741:Methyl Methanesulfonate / Q000633:toxicity; D008770:Methylnitrosourea / Q000633:toxicity; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D013311:Streptozocin / Q000493:pharmacokinetics* / Q000633:toxicity*; D014162:Transfection
D000477:Alkylating Agents; D051273:Glucose Transporter Type 2; D009004:Monosaccharide Transport Proteins; D011994:Recombinant Proteins; D019325:3-O-Methylglucose; D013311:Streptozocin; D008770:Methylnitrosourea; D005020:Ethyl Methanesulfonate; D008741:Methyl Methanesulfonate; D005038:Ethylnitrosourea