Only a few positive cells were found in lung sections from rats treated for 30 mins with LPS (Figure 10), with localization apparently different from those reacting with NOS-III-specific probe. Microscopic examination under a higher magnification (Figure 11) revealed that pulmonary vessels were filled with positive-stained cells, which may suggest that the cellular source of NOS-II, even at the beginning of the second phase of endotoxemia, was wandering cells (eg, macrophages or leukocytes) rather than induction of NOS-II in lung parenchyma.
Figure 10 In situ hybridization histochemistry of rat inducible nitric oxide synthase (NOS-II) mRNA in lungs 30 mins after lipopoly-saccharide infusion. Digoxigenine- (DIG) labelled 473 base pair cDNA probe was hybridized to tissue section and detected with an enzyme-link immunoassay as described in Animals and Methods. Staining with specific DIG-labelled cDNA probe showed rare, intense hybridized signals of NOS-II mRNA visualized by dark colour of formazan dispersed in lung parenchyma (arrows). Original magnification x100
Figure 11 Higher magnification (x400) of the microphotograph shown in Figure 10. Intense hybridized signals of inducible nitric oxide synthase transcripts in the lumen of vessels and in cells infiltrating lung parenchyma are seen (arrows)