Cardiac hypertrophy by pressure overload is preserved in MEKK1–/– mice. Transverse aortic banding or sham operation was applied in either control or MEKK1–/– mice. (a) Pressure gradient across the constriction at the transverse aorta was measured at 7 days. (b) LV weight (LVW) (mg)/body weight (BW) (g) was obtained at 7 and 14 days. *P < 0.001 vs. MEKK1+/+ mice with 14 days banding. (c) LVW (mg)/tibial length (TL) (mm) was obtained at 7 days. n = 5–10. (d) Cardiac myocyte cross-sectional area was obtained at 7 days. n = 5 for each group. The right panel shows the light micrographs of silver-stained 1-μm sections of LV myocardium from sham-operated and banded MEKK1–/– mice. (e) mRNA expression of atrial natriuretic factor (ANF) at 7 days was evaluated by Northern blot analyses. Densitometric analyses were performed. The mean of ANF/GAPDH in control mice subjected to 1 week of banding was expressed as 1. n = 5 for each group. NS, not significant.