RESUMO
Rat ear cartilage was studied using Fourier transform-infrared (FT-IR) microspectroscopy to expand the current knowledge which has been established for relatively more complex cartilage types. Comparison of the FT-IR spectra of the ear cartilage extracellular matrix (ECM) with published data on articular cartilage, collagen II and 4-chondroitin-sulfate standards, as well as of collagen type I-containing dermal collagen bundles (CBs) with collagen type II, was performed. Ear cartilage ECM glycosaminoglycans (GAGs) were revealed histochemically and as a reduction in ECM FT-IR spectral band heights (1140-820 cm-1) after testicular hyaluronidase digestion. Although ear cartilage is less complex than articular cartilage, it contains ECM components with a macromolecular orientation as revealed using polarization microscopy. Collagen type II and GAGs, which play a structural role in the stereo-arrangement of the ear cartilage, contribute to its FT-IR spectrum. Similar to articular cartilage, ear cartilage showed that proteoglycans add a contribution to the collagen amide I spectral region, a finding that does not recommend this region for collagen type II quantification purposes. In contrast to articular cartilage, the symmetric stretching vibration of -SO3- groups at 1064 cm-1 appeared under-represented in the FT-IR spectral profile of ear cartilage. Because the band corresponding to the asymmetric stretching vibration of -SO3- groups (1236-1225 cm-1) overlapped with that of amide III bands, it is not recommended for evaluation of the -SO3- contribution to the FT-IR spectrum of the ear cartilage ECM. Instead, a peak (or shoulder) at 1027-1016 cm-1 could be better considered for this intent. Amide I/amide II ratios as calculated here and data from the literature suggest that protein complexes of the ear cartilage ECM are arranged with a lower helical conformation compared to pure collagen II. The present results could motivate further studies on this tissue under pathological or experimental states involving ear cartilage.
Assuntos
Cartilagem Articular/metabolismo , Cartilagem da Orelha/metabolismo , Matriz Extracelular/metabolismo , Espectroscopia de Infravermelho com Transformada de Fourier , Animais , Sulfatos de Condroitina/metabolismo , Colágeno Tipo I/metabolismo , Colágeno Tipo II/metabolismo , Glicosaminoglicanos/metabolismo , RatosRESUMO
This experimental study demonstrates that iontophoresis can be used to transport biologically active gentamicin into auricular cartilage. Fifty female New Zealand White rabbits were divided into three groups: live controls with unburned ears, live animals with burn-injured ears (deep or partial-thickness), and euthanized animals with unburned ears. Each group was then divided into subgroups that received gentamicin transported by iontophoresis or diffusion. In ears subjected to iontophoresis, adequate gentamicin activity could be demonstrated only in the cartilage of euthanized animals with unburned ears and live animals with full-thickness burned ears. Diffusion did not transport a detectable level of gentamicin in any instance. Diffusion is ineffective in the transport of gentamicin and should not be used as a primary method of treatment for ear chondritis. Iontophoresis did not transport active gentamicin across partial-thickness burns, presumably because the migrating antibiotic molecules were dispersed throughout the body by the circulation. However, if the circulation is destroyed, as in a full-thickness burn, iontophoresis can move the biologically active gentamicin into the cartilage.