Diastolic function during hemorrhagic shock in rabbits

Hemorrhage (H) is associated with a left ventricular (LV) dysfunction. However, the diastolic function has not been studied in detail. The main goal was to assess the diastolic function both during and 120 min after bleeding, in the absence and in the presence of L-NAME. Also, the changes in mRNA and protein expression of nitric oxide synthase (NOS) isoforms were determined. New Zealand rabbits were divided into three groups: Sham group, H group (hemorrhage 20% blood volume), and H L-NAME group (hemorrhage treated with L-NAME). We evaluated systolic and diastolic ventricular functions in vivo and in vitro (Langendorff technique). Hemodynamic parameters and LV function were measured before, during, and at 120 min after bleeding. We analyzed the isovolumic relaxation using t ½ in vivo (closed chest). After that, hearts were excised and perfused in vitro to measure myocardial stiffness. Samples were frozen to measure NOS mRNA and protein expression. The t½ increased during bleeding and returned to basal values 120 min after bleeding. L-NAME blunted this effect. Data from the H group revealed a shift to the left in the LV end diastolic pressure-volume curve at 120 min after bleeding, which was blocked by L-NAME. iNOS and nNOS protein expression and mRNA levels increased at 120 min after the hemorrhage. Acute hemorrhage induces early and transient isovolumic relaxation impairment and an increase in myocardial stiffness 120 min after bleeding. L-NAME blunted the LV dysfunction, suggesting that NO modulates ventricular function through iNOS and nNOS isoforms.