Expression of nitric oxide synthase in the process of cerebral ischemia/reperfusion

Chao WANG; Feng SUN; Xiaojie DING

ABSTRACT

BACKGROUND:

Nitric oxide synthase(NOS) is the key factor for the synthesis of nitric oxide (NO) . Because NO combines with oxygen, hemoglobin and other substances in vivo easily and deactivates quickly, and it is not exactly determined, so determining the activity of NOS is the important link for further studying the pathogenesis of NO in cerebral ischemia/reperfusion (I/R)injury.

OBJECTIVE:

To study the effect of different types of NOS in the process of cerebral I/R injury.

DESIGN:

Randomized and controlled animal experiment.

SETTING:

Instituteof Cerebrovascular Disease, Affiliated Hospital of Medical College of Qingdao University.MATERIALS This experiment was carried out in the Shandong Key Laboratory of Prevention and Treatment for Encephalopathy from May to December 2005. Twenty-eight adult healthy male Wistar rats, of clean grade, weighing from 220 to 260 g, were provided by the Experimental Animal Center of Shandong University. The involved rats were randomly divided into sham-operation group (n =4) and cerebral ischemia group (n =24). Six time points were set in cerebral ischemia group ischemia 1 hour reperfusion 6 hours, 12 hours, 1 day, 3 days, 7 days and 14 days, 4 rats at each time point.

METHODS:

Rat models of middle cerebral artery occlusion/reperfusion were established by suture-occluded method through inserting a suture into the left internal-external carotid artery. The expressions of different types of NOS at different time points after cerebral I/R were detected by immunohistochemical technique.MAIN OUTCOME

MEASURES:

①Toluidine blue-stained two groups of nerve cells; ② The expression and distribution of neuronal NOS (nNOS), endothelial NOS (eNOS) and inducible NOS(iNOS) at different time points.

RESULTS:

①Karyopyknosis and cell debris appeared in the nerve cells of the injured region of cerebral ischemia group,and there were no significant differences of cells among different time points. ② Six hours after reperfusion, the expressions of nNOS, eNOS and iNOS were found in the neurons of brain tissue and increased with the elongation of time of reperfusion. The regions in which different types of NOS in neurons of brain tissue were expressed were cortical area and corpora striata. nNOS and iNOS were highly expressed within 12 hours to 7 days after reperfusion in the brain, and eNOS was highly expressed within a short time period, i.e. 6 hours to 3 days after reperfusion. eNOS expression increasing and decreasing occurred earlier than nNOS and iNOS. But the expressions of three kinds of NOS all reached peak on the first day after reperfusion. The changing tendencies of the expression of three kinds of NOS in the cortical area and corpora striata were the same basically.

CONCLUSION:

After cerebral I/R injury, the high expression of eNOS occurs early and lasts for a short time, while that of nNOS and iNOS occurs late and lasts for a long time.