We have recently succeeded in developing mice in which all three nitric oxide synthase isoforms (nNOS, iNOS, and eNOS) are completely disrupted (
PNAS
2005). In this study, we examined cardiac morphology and function in those mice. Cardiac echocardiography and left ventricular (LV) hemodynamic measurement were performed in male wild-type (WT), singly nNOS
−/−
, iNOS
−/−
, eNOS
−/−
, and triply n/i/eNOS
−/−
mice at 2 and 5 months of age (n=5–8). At 2 months of age, no significant cardiac morphological or functional changes were detected in any strains studied. However, at 5 months of age, significant LV hypertrophy (wall thickness, mm) were noted in the triply n/i/eNOS
−/−
mice (1.3±0.1,
P
<0.01) and to a lesser extent in the singly eNOS
−/−
mice (1.1±0.1,
P
<0.05), but not in the singly nNOS
−/−
(0.8±0.1) or iNOS
−/−
mice (1.0±0.1), as compared with the WT mice (1.0±0.2). Furthermore, significant LV diastolic dysfunction (as evaluated by echocardiographic E/A ratio and by hemodynamic peak negative dP/dt), with preserved LV systolic function (as assessed by echocardiographic ejection fraction and by hemodynamic peak positive dP/dt), was noted only in the 5-month-old triply n/i/eNOS
−/−
mice (2.7±0.1 and 2505±60, both
P
<0.05), but not in any singly nNOS
−/−
(2.1±0.2 and 3833±402), iNOS
−/−
(2.0±0.1 and 3773±747), or eNOS
−/−
mice (2.0±0.3 and 2934±122), as compared with the WT mice (1.9±0.1 and 4038±344). In addition, significant cardiac fibrosis (fibrosis area, %, Masson-trichrome staining) was also detected only in the 5-month-old triply n/i/eNOS
−/−
mice (1.4±0.2,
P
<0.05) compared with the WT mice (0.3±0.1). Importantly, arterial blood pressure (mmHg, tail-cuff method) was significantly elevated in the triply n/i/eNOS
−/−
(143±3.1,
P
<0.05) than in the WT mice (104±7.3), but the hypertensive level was comparable to that in the singly eNOS
−/−
mice (140±8.5). Thus, mechanism(s) other than hypertension appears to be involved in the cardiac abnormalities of the triply n/i/eNOS
−/−
mice. These results provide the first evidence that genetic disruption of all NOSs results in LV hypertrophy and diastolic dysfunction in mice in vivo, suggesting a pivotal role of the NOS system in maintaining cardiac homeostasis.
Angiotensin II is involved in nitric oxide synthase and cyclo-oxygenase inhibition-induced leukocyte-endothelialcell interactions in vivo
