Altered expression of insulins I and II and their mRNAs in the islets of Langerhans in dexamethasone-induced diabetic rats.
Rats have two isomeric insulins (insulins I and II). There have been no reports on the expression of the isomeric insulins in glucocorticoid-induced diabetic rats. To clarify the relation of the expression of each insulin and its mRNAs in dexamethasone-induced diabetic rats, the amounts of the isomeric insulins and mRNAs in the islets of Langerhans were determined in vivo and in vitro. A sensitive and selective HPLC-fluorescence determination method for the isomeric insulins and a newly developed real-time quantitative RT-PCR method for their mRNAs were used. There was a greater reduction of insulin II than insulin I in the islets of Langerhans in dexamethasone-induced diabetic rats. This alteration may be caused by a disproportionate expression of the respective mRNA for the isomeric insulins that resulted from the direct effect of dexamethasone. In addition, continuous hyperglycemia may also suppress the expression of the insulin II mRNA. The overall effects of dexamethasone and hyperglycemia may cause a greater reduction of insulin II than insulin I in the dexamethasone-induced diabetic rat. Conversely, an elevated ratio of insulin I to II in the islets could suggest a diabetic condition.
Toriumi
Chifuyu
C
Laboratory of Bio-Analytical Chemistry, Graduate School of Pharmaceutical Sciences, the University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Imai
Kazuhiro
K
D000818:Animals; D001483:Base Sequence; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D017931:DNA Primers; D003907:Dexamethasone / Q000494:pharmacology*; D005947:Glucose / Q000494:pharmacology; D007328:Insulin / Q000235:genetics* / Q000378:metabolism; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D012333:RNA, Messenger / Q000235:genetics*; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013050:Spectrometry, Fluorescence / Q000379:methods
D017931:DNA Primers; D007328:Insulin; D012333:RNA, Messenger; D003907:Dexamethasone; D005947:Glucose