Horseradish peroxidase permeability across rat nasal mucosa in selective stimulation of substance P innervation with capsaicin

Horseradish peroxidase: a valuable tool in biotechnology

Peroxidases have conquered a prominent position in biotechnology and associated research areas (enzymology, biochemistry, medicine, genetics, physiology, histo- and cytochemistry). They are one of the most extensively studied groups of enzymes and the literature is rich in research papers dating back from the 19th century. Nevertheless, peroxidases continue to be widely studied, with more than 2000 articles already published in 2002 (according to the Institute for Scientific Information). The importance of peroxidases is emphasised by their wide distribution among living organisms and by their multiple physiological roles. They have been divided into three superfamilies according to their source and mode of action: plant peroxidases, animal peroxidases and catalases. Among all peroxidases, horseradish peroxidase (HRP) has received a special attention and will be the focus of this review. A brief description of the three super-families is included in the first section of this review. In the second section, a comprehensive description of the present state of knowledge of the structure and catalytic action of HRP is presented. The physiological role of peroxidases in higher plants is described in the third section. And finally, the fourth section addresses the applications of peroxidases, especially HRP, in the environmental and health care sectors, and in the pharmaceutical, chemical and biotechnological industries.

Confocal laser scanning microscopic visualization of the transport of dextrans after nasal administration to rats: effects of absorption enhancers

PURPOSE

To visualize the transport pathway(s) of high molecular weight model compounds across rat nasal epithelium in vivo using confocal laser scanning microscopy. Furthermore, the influence of nasal absorption enhancers (randomly methylated beta-cyclodextrin and sodium taurodihydrofusidate) on this transport was studied.

METHODS

Fluorescein isothiocyanate (FITC)-labelled dextrans with a molecular weight of 3,000 or 10,000 Da were administered intranasally to rats. Fifteen minutes after administration the tissue was fixed with Bouin. The nasal septum was surgically removed and stained with Evans Blue protein stain or DiIC18(5) lipid stain prior to visualization with the confocal laser scanning microscope.

RESULTS

Transport of FITC-dextran 3,000 across nasal epithelium occurred via the paracellular pathway. Endocytosis of FITC-dextran 3,000 was also shown. In the presence of randomly methylated beta-cyclodextrin 2% (w/v) similar transport pathways for FITC-dextran 3,000 were observed. With sodium taurodihydrofusidate 1% (w/v) the transport route was also paracellular with endocytosis, but cells were swollen and mucus was extruded into the nasal cavity. For FITC-dextran 10,000 hardly any transport was observed without enhancer, or after co-administration with randomly methylated beta-cyclodextrin 2% (w/v). Co-administration with sodium taurodihydrofusidate 1% (w/v) resulted in paracellular transport of FITC-dextran 10,000, but morphological changes, i.e. swelling of cells and mucus extrusion, were observed.

CONCLUSIONS

Confocal laser scanning microscopy is a suitable approach to visualize the transport pathways of high molecular weight hydrophilic compounds across nasal epithelium, and to study the effects of absorption enhancers on drug transport and cell morphology.