Chronic L-arginine treatment increases cardiac cyclic guanosine 5'-monophosphate in rats with aortic stenosis: effects on left ventricular mass and beta-adrenergic contractile reserve.
OBJECTIVE
We tested the hypothesis that nitric oxide (NO) cyclic guanosine 5'-monophosphate (GMP) signaling is deficient in pressure overload hypertrophy due to ascending aortic stenosis, and that long-term L-arginine treatment will increase cardiac cyclic GMP production and modify left ventricular (LV) pressure overload hypertrophy and beta-adrenergic contractile response.


BACKGROUND
Nitric oxide cyclic GMP signaling is postulated to depress vascular growth, but its effects on cardiac hypertrophic growth are controversial.


METHODS
Forty control rats and 40 rats with aortic stenosis left ventricular hypertrophy ([LVH] group) were randomized to receive either L-arginine (0.40 g/kg/day) or no drug for 6 weeks.


RESULTS
The dose of L-arginine did not alter systemic blood pressure. Animals with LVH had similar LV constitutive nitric oxide synthase (cNOS) mRNA and protein levels, and LV cyclic GMP levels as compared with age-matched controls. In rats with LVH L-arginine treatment led to a 35% increase in cNOS protein levels (p = 0.09 vs untreated animals with LVH) and a 1.7-fold increase in LV cyclic GMP levels (p < 0.05 vs untreated animals with LVH). However, L-arginine treatment did not suppress LVH in the animals with aortic stenosis. In contrast, in vivo LV systolic pressure was depressed in L-arginine treated versus untreated rats with LVH (163 +/- 16 vs 198 +/- 10 mm Hg, p < 0.05). In addition, the contractile response to isoproterenol was blunted in both isolated intact hearts and isolated myocytes from L-arginine treated rats with LVH compared with untreated rats with LVH. This effect was mediated by a blunted increase in peak systolic intracellular calcium in response to beta-adrenergic stimulation.


CONCLUSIONS
Left ventricular hypertrophy due to chronic mechanical systolic pressure overload is not characterized by a deficiency of LV cNOS and cyclic GMP levels. In rats with aortic stenosis, L-arginine treatment increased cardiac levels of cyclic GMP, but it did not modify cardiac mass in rats with aortic stenosis. However, long-term stimulation of NO-cyclic GMP signaling depressed in vivo LV systolic function in LVH rats and markedly blunted the contractile response to beta-adrenergic stimulation.
Charles A. Dana Research Institute, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA.
J
J
Bartunek
S
S
Dempsey
E O
EO
Weinberg
N
N
Ito
M
M
Tajima
S
S
Rohrbach
B H
BH
Lorell
D000318:Adrenergic beta-Agonists / Q000008:administration & dosage / Q000627:therapeutic use*; D000818:Animals; D001024:Aortic Valve Stenosis / Q000188:drug therapy* / Q000378:metabolism; D001120:Arginine / Q000008:administration & dosage / Q000627:therapeutic use*; D001794:Blood Pressure / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D016022:Case-Control Studies; D006152:Cyclic GMP / Q000378:metabolism*; D006973:Hypertension / Q000150:complications; D017379:Hypertrophy, Left Ventricular / Q000188:drug therapy* / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D008137:Longitudinal Studies; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D013599:Systole; D016277:Ventricular Function, Left / Q000187:drug effects; D017725:Ventricular Pressure / Q000187:drug effects
D000318:Adrenergic beta-Agonists; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D006152:Cyclic GMP; D007545:Isoproterenol; D002118:Calcium