Protective effects of a calcium channel blocker on apoptosis in thymus of neonatal STZ-diabetic rats.
Streptozotocin (STZ) is known to induce insulin-dependent diabetes in experimental animals. In STZ-induced diabetes, atrophy of the thymus is caused by elevated intracellular calcium levels leading to apoptosis. Hyperglycemia is known to result in a decrease in numbers of T cells in the thymus and circulation. Intracellular calcium levels increase in diabetic animals after induction by STZ. Hyperglycemia inhibits Ca2+-ATPase and increases intracellular calcium levels. We have investigated apoptosis in thymus tissue of neonatal STZ (n-STZ)-diabetic rats and the effects of isradipine as a calcium channel blocker (CCB) on apoptosis. Five groups of newborn Wistar rats were used. On the second day after birth, 100 mg/kg STZ was given i.p. to the first two groups. The first group was n-STZ diabetic. To the second group, starting from the 12th week, 5 mg/kg/day isradipine (i.p) was given for 6 weeks. To the third group, the same dose of isradipine was given on the second day, followed by STZ treatment. The fourth group was non-diabetic and treated with 5 mg/kg/day isradipine for six weeks. The fifth group consisted of non-diabetic rats. To the sixth group, dexamethasone (5 mg/kg i.p.) was given to adult rats. For detection of apoptotic cells in paraffin-embedded thymus sections, the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling (TUNEL) assay was used. The DNA ladder method was performed for analysis of DNA fragmentation. In the isradipine-treated non-diabetic group, typical apoptotic banding patterns were found, whereas thick bands between 123 and 246 bp length were found in the n-STZ- and n-STZ+isradipine-treated groups. More apoptotic cells were observed in the thymus of isradipine-treated, n-STZ-treated and n-STZ+isradipine-treated groups when compared with the non-diabetic control and isradipine+n-STZ-treated groups. In conclusion, we observed that long-term STZ diabetes results in apoptosis in the thymus. We also found that isradipine administered before STZ has protective effects against apoptosis, whereas isradipine alone induces apoptosis.
Kaya Dağistanli
Fatma
F
Department of Medical Biology, Cerrahpasa Faculty of Medicine, Istanbul University, Cerrahpasa 34303, Istanbul, Turkey.
Süsleyici Duman
Belgin
B
Oztürk
Melek
M
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects*; D001786:Blood Glucose / Q000032:analysis; D002121:Calcium Channel Blockers / Q000627:therapeutic use*; D002452:Cell Count; D053938:DNA Fragmentation; D003907:Dexamethasone / Q000494:pharmacology; D003921:Diabetes Mellitus, Experimental / Q000097:blood / Q000188:drug therapy* / Q000473:pathology; D004195:Disease Models, Animal; D020287:In Situ Nick-End Labeling; D007274:Injections, Intraperitoneal; D017275:Isradipine / Q000627:therapeutic use*; D051381:Rats; D017208:Rats, Wistar; D013950:Thymus Gland / Q000187:drug effects* / Q000473:pathology
D001786:Blood Glucose; D002121:Calcium Channel Blockers; D003907:Dexamethasone; D017275:Isradipine