L-arginine improves endothelial and myocardial function after brain death

Abstract

Background: Recently, we showed that brain death (BD) leads to a severe impairment of endothelial function.

Methods: To test the hypothesis, that nitric oxide supply improves endothelial function, we infused L-arginine (40 mg/kg) in 6 dogs after BD induction (subdural balloon). Six vehicle-treated BD animals served as controls. Coronary blood flow (CBF), preload recruitable stroke work (PRSW), and plasma L-arginine and nitrite/nitrate levels were measured before and 6 hr after BD induction. In addition, endothelium-dependent vasodilatation after intracoronary application of acetylcholine (ACH) and endothelium-independent vasodilation after sodium nitroprusside (SNP) were assessed.

Results: Six hours after BD, CBF decreased significantly in the control group (38.2+/-3.5 vs. 26.8+/-3.1 ml/min, P<0.05), whereas the decrease was less pronounced in the L-arginine group (41.8+/-6.9 vs. 36.0+/-1.2 ml/min, P<0.05 vs. control). Before BD, ACH led to a similar vasodilative response in both groups (81+/-6 vs. 75+/-7%). After BD, a paradox vasoconstriction occurred after ACH in the control group, while the vasodilative response did not change in the L-Arginine group (36+/-6 vs. 69+/-7%, P<0.05). The response to SNP did not differ between the groups and over the time. After BD PRSW decreased in both groups, however, it was still significantly higher in the L-arginine group (56+/-7 vs. 71+/-7 kerg, P<0.05). L-arginine (711+/-144 vs. 234+/-54 microM P<0.05) and nitrite/nitrate (39+/-3 vs. 27+/-3 microM P<0.05) levels were significantly higher in the L-arginine group.

Conclusion: L-arginine treatment prevents endothelial dysfunction and improves myocardial performance after BD via enhancement of endogenous nitric oxide synthesis.