Time Course of Changes in Nitric Oxide Synthases Following Subarachnoid Hemorrhage in Primates
Nitric oxide (NO) may be important in vasospasm following subarachnoid hemorrhage (SAH). We evaluated the time course of changes in 3 isoforms of NO synthase (NOS) after SAH in monkeys. Right SAH was created and vasospasm was assessed on angiograms obtained at baseline and after 3, 7 and 14 days. Animals were euthanized at these times (n = 4 - 6 per time) and the right and left (control) middle cerebral arteries were removed. Levels of nNOS, eNOS and iNOS messenger ribonucleic acid (mRNA) and protein were measured by reverse transcriptase polymerase chain reaction and Western blotting. Angiography showed a 45 ± 13% (mean ± s.d., p < 0.05) decrease in middle cerebral artery diameter 3 days, a 41 ± 23% (p< 0.05) decrease 7 days and an insignificant 6 ± 14% decrease 14 days after SAH. The RNA for eNOS was significantly reduced (1.7 ± 0.5-fold) 7 days after SAH. There was a significant, 1.7 ± 0.2-fold reduction in eNOS protein on days 3 and 7 after SAH that returned to normal by day 14. There were no significant changes in nNOS mRNA or protein at any time after SAH. There were no significant changes in iNOS mRNA whereas iNOS protein increased on days 3 and 7 (7 ± 9 and 2.7 ± 2.8-fold, respectively, p > 0.05) and significantly decreased (2.7 ± 1.1-fold, p < 0.05) on day 14. Immunohistochemistry localized eNOS to endothelium, nNOS to brain and perivascular adventitia of the middle cerebral arteries and iNOS to inflammatory cells in the subarachnoid space. These results show a correlation between decreased eNOS and increased iNOS during vasospasm, suggesting a complex role for changes in NO in vasospasm.