Expression of endothelial nitric oxide synthase after exposure to perivascular blood.

ABSTRACT

OBJECTIVE: Although nitric oxide (NO) has been implicated in the development of vasospasm after subarachnoid hemorrhage, little is known regarding the time course of NO synthesis in vessel wall after exposure to perivascular blood. This study measures temporal characteristics of changes in vessel wall NO synthesis. METHODS: Rat femoral arteries exposed to perivascular blood for 3, 5, or 7 days were assayed for the endothelial isoform of NO synthase (eNOS) by Western blot testing. Additionally, rat femoral arteries exposed to perivascular blood for intervals from 3 to 14 days were analyzed by means of immunohistochemistry for eNOS. RESULTS: Semiquantitative densitometry of femoral artery Western blots demonstrated a biphasic pattern of eNOS expression after exposure to perivascular blood. Compared with control arteries, eNOS expression increased at 3 days (53 +/- 36%), normalized at 5 days (-6 +/- 7%), and decreased by 7 days (-39 +/- 15%). Immunohistochemistry confirmed the changes in expression of immunoreactive eNOS in femoral endothelium during the first week after chronic perivascular blood exposure and apparent reduced eNOS immunostaining, which persisted up to 14 days after application of blood. CONCLUSION: The expression of endothelial-derived NO in rat femoral artery exposed to perivascular whole blood does not directly correlate with changes in vessel caliber during this interval. The biphasic expression of eNOS observed in these experiments highlights the complexity of processes occurring in the vicinity of the vessel wall during vasospasm and may be related to several mechanisms that modulate vessel tone and response to injury.