3.3 Presence of NO-synthases and antioxidant enzymes
Endothelial NO-synthase (eNOS or NOS3) was detected with immunohistochemistry in most arteries investigated (Figure 3A). The staining was faint, unevenly distributed over the arterial wall, not restricted to the luminal endothelial layer but present in the tunica media as well. Largely similar staining for eNOS was observed in small arteries in the atrial appendage fixed immediately after isolation during surgery (Figure 3B). This control was performed to exclude that expression of eNOS had been modified during several hours of in vitro investigation of the isolated resistance arteries investigated.
The other isozymes of NO-synthase were expressed as well in the resistance arteries of the CVD patients. As was the case for eNOS, staining of inducible NO-synthase (iNOS or NOS2) was faint, unevenly distributed over the microvascular wall and detected in both endothelial and smooth muscle cells (Figure 3C). Even though not directly comparable due to the nature of the IHC, expression of neuronal NO-synthase (nNOS or NOS1) was easily detectable, and thus seemed more abundant in the resistance artery endothelium and smooth muscle compared to the other NO-synthases and was often detectable in the tunica adventitia as well (Figure 3D).
Endogenous catalase and Cu-Zn superoxide dismutase (SOD1) were detected in far less patients compared to the NO-synthases and both were observed primarily in the arterial smooth muscle cells (Figure 3E and 3F).