Gender-specific patterns of left ventricular and myocyte remodeling following myocardial infarction in mice deficient in the angiotensin II type 1a receptor

Left ventricular (LV) remodeling after myocardial infarction (MI) results from hypertrophy of myocytes and activation of fibroblasts induced, in part, by ligand stimulation of the ANG II type 1 receptor (A[T.sub.1]R). The purpose of the present study was to explore the specific role for activation of the A[T.sub.1a]R subtype in post-MI remodeling and whether gender differences exist in the patterns of remodeling in wild-type and A[T.sub.1a]R knockout (KO) mice. A[T.sub.1a]R-KO mice and wild-type littermates underwent coronary ligation to induce MI or sham procedures; echocardiography and hemodynamic evaluation were performed 6 wk later, and LV tissue was harvested for infarct size determination, morphometric measurements, and gene expression analysis. Survival and infarct size were similar among all male and female wild-type and A[T.sub.1a]R-KO mice. Hemodynamic indexes were also similar except for lower systolic blood pressure in the A[T.sub.1a]R-KO mice compared with wild-type mice. Male and female wild-type and male A[T.sub.1a]R-KO mice developed similar increases in LV chamber size, LV mass corrected for body weight (LV/BW), and myocyte cross-sectional area (CSA). However, female A[T.sub.1a]R-KO mice demonstrated no increase in LV/BW and myocyte CSA post-MI compared with shams. Both male and female wild-type mice demonstrated higher atrial natriuretic peptide (ANP) levels after MI, with female wild types being significantly greater than males. However, male and female A[T.sub.1a]R-KO mice developed no increase in ANP gene expression with MI despite an increase in LV mass and myocyte size in males. These data support that gender-specific patterns of LV and myocyte hypertrophy exist after MI in mice with a disrupted A[T.sub.1a]R gene, and suggest that myocyte hypertrophy post-MI in females relies, in part, on activation of the A[T.sub.1a]R. Further work is necessary to explore the potential mechanisms underlying these gender-based differences. angiotensin II receptors; ventricular remodeling; myocyte; hypertrophy