[Ultrastructural localization of nitric oxide synthase (NOS I and III) in human nasal mucosa]

Nasal vasculature and seromucous glands are exposed to complex mechanisms influenced by external as well as internal stimuli. In addition to classic and peptidergic neurotransmitters, Nitric oxide (NO) was increasingly found to be important in the control of various physiological functions. NO regulates nasal immunology, influences macrophages activity and has antiviral and bacteriostatic properties. The aim of this study was to detect the localization of nitric oxide synthases (NOS) I and III in the normal human nasal mucosa with immunoelectron microscopical techniques.

Specimens of non-inflamed inferior turbinates from 35 patients who required nasal surgery were fixed in phosphate-buffered glutaraldehyde. After dehydration, incubation in unicryl and polymerization ultrathin sections were cut. Primary antibodies against NOS I and III were applied and the immunocomplexes were visualized by an immunocytochemical staining-technique using a gold-labeled antibody. Immunostained structures were photodocumented by using a transmission electron microscope.

NOS-immunoreactive nerve fibers were mainly colocated in parasympathetic nerves in the adventitia of arterial vessels and in periglandular axons. Electron microscopy showed that NOS-positive axons were in close contact with acinus cells. A strong NOS III-immunoreactivity was found in endothelial cells of capillaries near the glands as well as in arterial vessels. Furthermore, immunoreaction products were deposited throughout the cytoplasm of fibroblasts.

Nitric oxide in nerval fibers, seromucous glands and endothelial cells of capillaries and arterial vessels suggests that NO takes part in the regulation of physiological processes of the human nasal mucosa. NO was colocalized in parasympathetic nerves and plays a role in the neurotransmission and neuromodulation of the vascular tone and glandular secretion. Arteries showed a distinctly developed nitric innervation and endothelial accumulation. The NO production in axons of the adventitia and in the endothelium of arteries demonstrated that these vessels are influenced by a dual NO system. Mainly NO could act on these structures with vasodilatory effects. Finally NO would be able to influence the functions of perivascular fibroblasts.