Hypertension-induced left ventricular (LV) hypertrophy is an independent risk factor for heart failure. To understand the impact of LV hypertrophy on cardiac hemodynamic before heart failure development, we studied LV performance and nitric oxide (NO) and reactive oxygen species (ROS) signaling in 6-month-old SHRs and age-matched Wistar-Kyoto rats (WKY) subjected to preload and afterload challenges. SHRs exhibited higher LV weight, LV developed pressure (LVDP), LV end-systolic pressure (LVESP),

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... rate of rise (LV dp/dt max ) and fall (LV dp/dt min ) in LV pressure. Further, LV nNOS, but not eNOS, expression and nitrite/nitrate (NOx) were higher in SHRs than WKYs. Acute volume overload (dextrose infusion) caused smaller reductions in LV dp/dt max and LVDP and greater increases in LVEDP and isovolumic relaxation constant (Tau, τ) in SHRs, compared with WKYs, suggesting a better preserved systolic and depressed diastolic functions in SHRs. SHRs exhibited improved LV performance during pressure overload (phenylephrine infusion) as reflected by the greater increases in LVDP, LVESP, LV dp/dt min , and LV dp/dt max . LV ROS was increased by overload challenges in WKYs but not in SHRs. Overall, the blunted increase in LV ROS may account for the betterpreserved ventricular performance during volume or pressure overload in SHRs despite evidence of early LV hypertrophy. In the current study, we tested the hypothesis that early LV hypertrophy in hypertensive rats alters LV performance in response to overload challenges. Accordingly, integrative cardiovascular studies were undertaken to evaluate LV function in 6-month-old conscious SHRs and age-matched WKY rats in response to volume or pressure overload challenges, which greatly impact LV performance [21] . The integrative studies were complemented with molecular studies to delineate the role of LV NOS expression/activity, and ROS level in LV performance at baseline and following pressure or volume overload in SHRs and in their controls. The data reported in this communication have been previously presented in the "Experimental Biology" meeting (EB2013) and published in an abstract form [22] . Materials and Methods Age-matched (22-24 weeks) male SHR and WKY rats were obtained from Charles River (Raleigh, NC). Rats were acclimatized to laboratory conditions (23°C, 12h/12h light/dark, 50% humidity,