[Effects of glibenclamide on mRNA level of ATP-sensitive potassium channels of heart in normal and streptozotocin-induced diabetic rats].
OBJECTIVE
To estimate if any difference exists in mRNA expression levels of KATP (SUR1, SUR2, Kir6.2) in heart tissues between streptozotocin-induced diabetic and normal rats, and to examine if any changes of heart KATP in mRNA level occurred after long-term Glibenclamide administration among the diabetic and control rats.


METHODS
Part 1: Adult male Sprague-Dawley (SD) rats were allocated into three groups: one group (n = 13) was taken as normal control, and the other two groups were diabetic models induced by a single intraperitoneal injection of streptozotocin (60 mg/kg). One of the diabetic groups (n = 10) was treated with premixed insulin (30%RI, 70%NPH) 4 - 8 units/day by subcutaneous injection at 4 - 5 pm everyday for two weeks. Part 2: Four groups of adult male SD rats were enrolled into the study. Group one (D1) was diabetes control induced by streptozotocin (n = 9), group two (DG2) was the diabetes treated with Glibenclamide (n = 14). Group three (N3) was normal control (n = 10), and group four (NG4) received Glibenclamide administration without diabetes (n = 14). DG2 and NG4 were given 10 mg/kg Glibenclamide intraperitonealy at 4 - 5 pm everyday for 14 days. Single-stranded digoxigenin-labeled probes were generated with RT-PCR. A total of 30 microgram of unfractionated RNA was transferred onto nylon membranes by dot-blot. Hybridization was performed at 50 degrees C for 16 hours with high SDS concentration hybridization buffer.


RESULTS
Study one: There was no significant difference in mRNA expression levels of SUR1, SUR2, and Kir6.2 in heart between diabetic, insulin-treated diabetic and control groups (P > 0.05). Study two: Glibenclamide-treated non-diabetic rats had higher mRNA expression levels of SUR1 and SUR2 in heart than normal control. The SUR1 were 43.0 +/- 16.6 vs 30.8 +/- 7.8 (P < 0.05), SUR2 161.9 +/- 51.0 vs 118.9 +/- 40.9 (P < 0.05), respectively. No difference in heart Kir6.2 mRNA level was found between the two groups (P > 0.05). Comparison between Glibenclamide-treated diabetic and non-treated diabetic rats showed that there was no change in mRNA levels of SUR1, SUR2 and Kir6.2 in heart (P > 0.05).


CONCLUSIONS
Chronic Glibenclamide-treatment up-regulates KATP gene transcriptional expression of heart in non-diabetic rats. The Streptozotocin-inducing diabetes itself does not affect the mRNA expression of KATP (SUR1, SUR2, and Kir6.2) in extra-pancreas tissues, but decreases the response of KATP to chronic Glibenclamide-treatment at transcriptional level.
Li
Y
Y
Department of Endocrinology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University of Medical Sciences, Guangzhou 510120, China.
Deng
Q
Q
Fu
Z
Z
D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000235:genetics* / Q000473:pathology; D005786:Gene Expression Regulation / Q000187:drug effects; D005905:Glyburide / Q000494:pharmacology*; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D008297:Male; D015221:Potassium Channels / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation / Q000187:drug effects
D007004:Hypoglycemic Agents; D015221:Potassium Channels; D012333:RNA, Messenger; D000255:Adenosine Triphosphate; D005905:Glyburide