The effects of folic acid and nitric oxide synthase inhibition on coronary flow and oxidative stress markers in isolated rat heart

The aim of this study was to assess the effects of folic acid on coronary flow and oxidative stress markers with or without non-specific inhibition of nitric oxide synthase by L-NAME in isolated rat hearts. The hearts of male Wistar albino rats (n = 12, age 8 weeks, body mass 180-200 g) were retrograde perfused according to the Langendorff technique at gradually increased constant perfusion pressure (40-120 cmH(2)O). Coronary flow and markers of oxidative stress: nitrite outflow, superoxide anion production, and index of lipid peroxidation (by measuring thiobarbituric acid reactive substances) in coronary effluent were calculated. The experiments were performed during control conditions and in presence of folic acid (100 mu M) alone or folic acid (100 mu M) plus L-NAME (30 mu M). Control values of coronary flow varied in range from 4.37 +/- 0.10 ml/min/g wt at 40 cmH(2)O to 12.05 +/- 0.42 ml/min/g wt at 120 cmH(2)O. Nitrite outflow varied from 1.68 +/- 0.17 nmol/min/g wt at 40 cmH(2)O to 3.56 +/- 0.17 nmol/min/g wt at 120 cmH(2)O and was parallel with coronary perfusion pressure-coronary flow curve. Folic acid significantly increased coronary flow (40-120 cmH(2)O, 5.63 +/- 0.10 ml/min/g wt and 15.2 +/- 0.42 ml/min/g wt, respectively) and was accompanied by significant increase in nitrite outflow (2.28 +/- 0.29 nmol/min/g wt at 40 cmH(2)O to 6.66 +/- 0.50 nmol/min/g wt at 120 cmH(2)O). In addition, folic acid significantly decreased superoxide anion production especially at upper coronary perfusion pressure values (60% at 120 cmH(2)O) and increased index of lipid peroxidation (37.16% at 120 cmH(2)O), respectively. Folic acid plus L-NAME did not change control values of coronary flow significantly. However, folic acid plus increased nitrite outflow especially at upper coronary perfusion pressure values (43.05% at 120 cmH(2)O) and did not change significantly superoxide anion production or index of lipid peroxidation versus control values, respectively. The results clearly showed that on isolated rat hearts at gradually increased constant perfusion pressure, folic acid increased coronary flow, increased nitrite outflow, decreased superoxide anion production, and increased index of lipid peroxidation. These effects were reversed or blocked by L-NAME thus demonstrating mediation or at least participation of NO in the mechanism of the folic acid-induced effects.