Cardiac gene expression of natriuretic substances is altered in streptozotocin-induced diabetes during angiotensin II-induced pressure overload.
OBJECTIVE
To gain insight into the cardiac adaptive mechanisms in diabetes, we studied whether angiotensin II (Ang II) alters expression of the atrial natriuretic peptide (ANP), B-type natriuretic peptide (BNP) and adrenomedullin (AM) genes in the left ventricle of the diabetic rat heart.


METHODS
Diabetes was induced by streptozotocin (STZ; 60 mg/kg body weight intravenously). During the last 24 h of 2.5 or 7 weeks of treatment of male Wistar rats with STZ or vehicle, Ang II (33 microg/kg per h) was administered via osmotic minipumps.


RESULTS
Diabetes was associated with an increased left ventricular weight to body weight (LV/BW) ratio, an index of left ventricular hypertrophy, at week 7 but not at week 2.5, and with increased ANP mRNA content at 2.5 weeks, but not with altered expression of the AM and BNP genes. Mean arterial pressure and LV/BW ratio were increased by Ang II in all groups except in the 7-week diabetic group. Levels of ANP mRNA were increased fourfold (P < 0.001) and threefold (P < 0.05) by Ang II at 2.5 and 7 weeks in control animals, respectively, and 11-fold (P < 0.001) and sevenfold (P < 0.001) at 2.5 and 7 weeks in diabetic animals, respectively. Ang II increased ventricular concentrations of BNP mRNA in control and diabetic animals at 2.5 weeks (1.3-fold, P < 0.001; and 1.6-fold, P < 0.001) and at 7 weeks (1.3-fold, P < 0.05; and 1.8-fold, P < 0.001), respectively. Left ventricular levels of adrenomedullin mRNA were increased by treatment with Ang II for 24 h in 2.5-week diabetic animals.


CONCLUSIONS
Ang II markedly increased the levels of natriuretic peptide mRNAs in the left ventricle of normal and diabetic rat hearts, whereas it increased adrenomedullin mRNA levels only in 2.5-week diabetic rats and failed to cause hypertension in 7-week diabetic rats. Left ventricular levels of ANP and BNP mRNA were increased by Ang II in diabetic animals more than the additive effects of diabetes and Ang II alone, showing that Ang II induced an amplified response with respect to cardiac concentrations of ANP and BNP in diabetes.
Ruzicska
Eva
E
2nd Department of Internal Medicine, Semmelweis University, Budapest, Hungary. ruzeva@bel2.sote.hu
Foldes
Gabor
G
Lako-Futo
Zoltan
Z
Sarman
Balazs
B
Wellmann
Janos
J
Szenasi
Gabor
G
Tulassay
Zsolt
Z
Ruskoaho
Heikki
H
Toth
Miklos
M
Somogyi
Aniko
A
D053607:Adrenomedullin; D000804:Angiotensin II / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000959:Antihypertensive Agents / Q000378:metabolism; D009320:Atrial Natriuretic Factor / Q000235:genetics / Q000378:metabolism*; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D006352:Heart Ventricles / Q000378:metabolism*; D017379:Hypertrophy, Left Ventricular / Q000378:metabolism*; D008297:Male; D020097:Natriuretic Peptide, Brain / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D015854:Up-Regulation
D000959:Antihypertensive Agents; D010455:Peptides; D012333:RNA, Messenger; D000804:Angiotensin II; D020097:Natriuretic Peptide, Brain; D053607:Adrenomedullin; D009320:Atrial Natriuretic Factor