Korean J Otolaryngol-Head Neck Surg.  2000 Feb;43(2):164-168.

Nitric Oxide Synthase Inhibitor Inhibits Platelet Activating Factor: Induced Microvascular Leakage in Rat Nasal and Tracheal Mucosa

• Kim CG
• Jeon SY
• Hwang EG
• Jung TG
• Kim HS
• Kang JY

Abstract

BACKGROUND AND OBJECTIVE
Platelet-activating factor (PAF), a potent chemical mediator in inflammation and allergic reaction, induces microvascular leakage in several tissues. In rat airways, PAF-induced microvascular leakage is not dependent on cyclooxygenase or lipoxygenase products nor on circulating platelets, and it is probably mediated by receptors on vascular endothelium. Nitric oxide (NO), first identified as endothelium-derived relaxing factor, has been reported recently to be an important mediator of the neurogenic vascular exudative process. The aim of this study was to investigate the role of NO in PAF-induced microvascular leakage in rat nasal and tracheal mucosa.
METHODS
PAF (1 ug/kg) was injected intravenously to induce microvascular leakage. The degree of microvascular leakage was measured with the amount of extravasated Evans blue (30 mg/kg) using both spectrophotometry and fluorescence microscopy. Five Sprague-Dawley rats were pretreated with Nw-nitro-L -arginine methyl ester (L-NAME, 10 mg/kg, intravenously, 1 hour before the injection of PAF) to inhibit the NO synthase, while four control rats(n=4) were pretreated with normal saline. RESULT: The average amounts of extravasated Evans blue in the nasal mucosa and trachea of the control rats were 24.789 and 28.238 ug/mg wet tissue, and those of the L-NAME pretreated rats were 6.643 and 6.987 ug/mg wet tissue respectively. Tissue sections of the L-NAME pretreated rats showed a definitely decreased extravasation of Evans blue under fluorescence microscopy.
CONCLUSION
Pretreatment with L-NAME clearly inhibited PAF-induced microvascular leakage in the nasal and tracheal mucosa of rat. This finding implies that NO may mediate PAF-induced microvascular leakage in rat airways.

Keyword

Platelet-activating factor(PAF); Microvascular leakage; Nitric oxide; Nitric oxide synthase; Nasal mucosa; Trachea

MeSH Terms

Animals
Blood Platelets*
Endothelium, Vascular
Endothelium-Dependent Relaxing Factors
Evans Blue
Hypersensitivity
Inflammation
Lipoxygenase
Microscopy, Fluorescence
Mucous Membrane*
Nasal Mucosa
NG-Nitroarginine Methyl Ester
Nitric Oxide Synthase*
Nitric Oxide*
Platelet Activating Factor*
Prostaglandin-Endoperoxide Synthases
Rats*
Rats, Sprague-Dawley
Spectrophotometry
Trachea
Endothelium-Dependent Relaxing Factors
Evans Blue
Lipoxygenase
NG-Nitroarginine Methyl Ester
Nitric Oxide
Nitric Oxide Synthase
Platelet Activating Factor
Prostaglandin-Endoperoxide Synthases