In a rat model of long-lasting pressure-overload hypertrophy, we investigated whether changes in the relative expression of myocardial actin isoforms are among the early signs of ventricular mechanical dysfunction before the transition toward decompensation. Forty-four rats with infra-renal aortic banding (AC rats) were studied. Hemodynamic parameters were measured one month (AC₁ group; n=20) or two months (AC₂; n=24) after aortic ligature. Then, subgroups of AC₁ and AC₂ left ventricles (LV) were used to evaluate: a) LV anatomy and fibrosis (morphometry), b) expression levels (immunoblotting) and spatial distribution (immunohistochemistry) of alpha-skeletal actin (-SKA), alpha-cardiac actin (-CA) and alpha-smooth muscle actin (-SMA), and c) cell mechanics and calcium transients, in enzimatically-isolated myocytes. Although the two AC groups exhibited a comparable degree of hypertrophy (+30% in LV mass; +20% in myocyte surface) and a similar increase in the amount of fibrosis as compared with control animals (C group, n=22), a worsening of LV mechanical performance was observed only in AC₂ rats, at both organ and cellular levels. Conversely, AC₁ rats exhibited enhanced LV contractility and preserved cellular contractile behavior associated with increased calcium transients. Alpha-SKA expression was up-regulated (+60%) in AC₁. In AC₂ ventricles, prolonged hypertension also induced a significant increase in -SMA expression, mainly at the level of arterial vessels. No significant differences among groups were observed in -CA expression. Our findings suggest that -SKA expression regulation and wall remodeling of coronary arterioles participate in the development of impaired kinetics of contraction and relaxation in prolonged hypertension, before the occurrence of marked histopathologic changes.