Figure 4.

The left panel shows eNOS protein expression and the right panel shows iNOS protein expression measured at baseline (BL), at 10 min of ventricular fibrillation (VF = 10 min), and serially after resuscitation at 30 min (PR = 30 min), at 2 h (PR = 2 h), and at 5 h (PR = 5 h). Data indicate that eNOS is expressed at baseline and diminished after just 10 min of cardiac arrest. Resuscitation appears to induce eNOS protein expression as shown in the third row, left panel (PR = 30 min). Then, eNOS expression appears to stabilize, then decrease by 5 h compared to 30 min after resuscitation. In contrast, no iNOS is detected at baseline (first row, right panel). Likewise, in contrast to eNOS, significant iNOS protein expression is evident after 10 min of VF cardiac arrest (second row, right panel). Similar to eNOS, iNOS protein expression appears to be induced by resuscitation, but iNOS expression appears to increase incrementally throughout the 5 h post-resuscitation period. Thus, it appears that eNOS and iNOS respond differently to cardiac arrest, while resuscitation seems to induce both nitric oxide synthase isoenzymes with an early, robust upregulation of eNOS and a slower, more sustained upregulation of iNOS.