BACKGROUND - Cardiac surgery can result in left ventricular ischemia and reperfusion (I/R), the release of cytokines such as tumor necrosis factor, and oxidative stress with release of myeloperoxidase. Although aprotinin has been used in cardiac surgery, the likely multiple effects of this serine protease inhibitor limit clinical utility. This study tested the hypothesis that different aprotinin doses cause divergent effects on left ventricular contractility, cytokine release, and oxidative stress in the context of I/R.
METHODS - Left ventricular I/R (30 minutes I, 60 minutes R) was induced in mice, and left ventricular contractility (maximal end-systolic elastance) determined. Mice were randomly allocated to 2 x 10(4) kallikrein inhibitory units (KIU)/kg aprotinin (n = 11), 4 x 10(4) KIU/kg aprotinin (n = 10), and vehicle (saline, n = 10). Based upon a fluorogenic assay, aprotinin doses of 2 and 4 x 10(4) KIU/kg resulted in plasma concentrations similar to those of the half and full Hammersmith doses, respectively.
RESULTS - After I/R, maximal end-systolic elastance fell by more than 40% from baseline (p < 0.05), and this effect was attenuated by 2 x 10(4) KIU/kg but not 4 x 10(4) KIU/kg aprotinin. Tumor necrosis factor increased by more than 60% from control (p < 0.05) with I/R, but was reduced with 4 x 10(4) KIU/kg aprotinin. Myeloperoxidase increased with I/R, and was reduced to the greatest degree by 2 x 10(4) KIU/kg aprotinin.
CONCLUSIONS - Aprotinin influences left ventricular contractility, cytokine release, and oxidative stress, which are dose dependent. These results provide mechanistic evidence that multiple pathways are differentially affected by aprotinin in a context relevant to cardiac surgery.