About 10% to 20% of the mice do not get diabetes. How can I improve the quality of work؟
Hello, could you tell us the sex and age of the animals so we can help you? Also, tell us about the route of administration of the drug. What is the diet of animals? Prior to the administration of streptozotocin, the rats have fasted? Have animals received insulin or glucose at any time after the administration of streptozotocin?
Thank you for your answer, streptozotocin 65 mg/kg/mL in 10 mM citrate buffer were used. male Wistar rats (8 weeks old), STZ injected via intraperitoneal , 12 h fasted prior to the administration and they haven't receive insulin or glucose after the administration of streptozotocin
Hi!!
Streptozotocin should be administered immediately after of being prepared, it must be at room temperature and it is very important to verify that the citrate buffer is at a pH of 4.5. Most of the times the problem is due to administration failures, please be sure to make a 45 degrees angle when administering intraperitoneally. Once you have had practice, between 80 and 90% of the animals become diabetic. Good luck!!!
Streptozotocin
STZ [2-deoxy-2-(3-(methyl-3-nitrosoureido)-d-glucopyranose] is synthesized by Streptomycetes achromogenes. After i.p. or i.v. administration, it enters the pancreatic beta cell through the Glut-2 transporter and causes alkylation of the DNA. Subsequent activation of PARP leads to NAD+ depletion, a reduction in cellular ATP and subsequent inhibition of insulin production . In addition, STZ is a source of free radicals that can also contribute to DNA damage and subsequent cell death. STZ tends to be administered as a single high dose or as multiple low doses.
High-dose STZ
The dose for a single high dose in mice ranges from 100 to 200 mg·kg−1, depending on the mouse strain, and in rats 35–65 mg·kg−1 . This leads to a rapid ablation of the beta cells and hyperglycaemia. It should be noted, however, that it has been suggested that regeneration of the pancreatic islets can occur after STZ treatment; and thus sufficient controls should be in place to determine that any improvement in glycaemia is not due to spontaneous regeneration of endogenous beta cells. High-dose STZ is often used in transplantation models, where islets or putative stem cells are transplanted under the kidney capsule. It should be noted that STZ has recently been shown to cause lymphopenia and a relative increase in T-regulatory cells, which could interfere with the interpretation of studies involving immune tolerance to transplants.
Multiple low-dose STZ
STZ can be administered as multiple low doses over 5 days to induce insulitis in mice or rats. Doses range from 20 to 40 mg·kg−1 per day, depending on the species and strain. A reduction in islet number and volume is apparent with concomitant reduction in insulin secretion capacity. Macrophages are the first cells to infiltrate the islets, and the development of diabetes is dependent on cytokine production . Diabetes develops even in the absence of T and B cells, and therefore, it does not model the human disease as closely as spontaneous models of autoimmunity. Therapies targeting cytokines and NO tend to be successful in reducing diabetes development in this model, indicating their role in the beta cell destruction.
Hello, your protocol is good and is the most used by authors from different research centers. Its failure rate in inducing diabetes with strepzotocin is within the acceptable range. Unfortunately not all animals develop the disease. You could apply strepzotocin to females because they are more susceptible to the development of diabetes ( a suggestion). In our laboratory, when a single dose of strepzotocin is not sufficient to induce diabetes in rats, we applied a second dose (half the initial dose). The second dose may be administered intraperitoneally, but our preference is for the intravenous route, because the results are better (rats are anesthetized, cannulated, and strepzotocin is injected into the tail vein).
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