[Regulation of the swelling mechanism in the inferior turbinate of human nasal mucosa].

BACKGROUND: The swelling mechanism of human nasal mucosa is based on a complicated vascular system and regulated by a variety of classical and peptidergic transmitters as well as by endothelial transmitters. The aim of this study was to elucidate this mechanism taking into account the distribution of these substances and the morphology of the different vessels.
METHODS: Tissue specimens of human inferior turbinates were evaluated by light and electron microscopy. We used frozen sections to localize enzymes of the transmitter synthesis by histochemical and immunocytochemical methods. The distribution of classical neurotransmitters, neuropeptides (calcitonin-gene-related-peptide, neuropeptide Y, substance P and vasoactive intestinal polypeptide), enzymes producing neuronal NO (neuronal nitric oxide synthase, nicotine-amid-adenine-dinucleotide-phosphate-diaphorase) as well as endothelial transmitters such as endothelin and endothelial nitric oxide were examined. For ultrastructal examination the specimens were fixed in glutaraldehyde und osmium tetroxide, embedded in araldide, cut and double contrasted.
RESULTS: Most of the axons and immunoreactivity of transmitters were located in the arterial part of the human nasal vascular system. In venous vessels only a spare innervation was observed, whereas in the subendothelial muscular bolsters of the cushion veins a rich nerve supply could be detected. Near the fenestrated subendothelial and periglandular capillaries no axons were found. Nasal vasculature is supplied by a equilibrated aminergic and cholinergic innervation. Mainly arterial vessels showed reactions to antibodies directed against endothelial transmitters.
CONCLUSION: Because of the dense innervation of arteries and subendothelial venous muscular bolsters we conclude that the swelling mechanism of human nasal mucosa is mainly regulated by these structures. A dual (endothelial and neuronal) control exists in arterioles whereas the control in the subendothelial muscular swellings of the cushion veins appears to be mainly neuronal. The swelling of the nasal mucosa is achieved by an simultaneous relaxation of all smooth muscle cells, which leads to dilatation of arteries as well as venous sinuses. The drainage of the vascular bed is reduced by the venous muscular bolsters protruding into the lumen of the venous sinuses. Vice versa, a contraction of all smooth muscle cells leads to a contraction of the arteries and, consecutively, to a reduction of blood supply. Simultaneously the muscular bolsters are torn out of the lumen of venous sinusoids allowing blood drainage to be increased: nasal concha decongests.