A comparison of acidic glycosaminoglycans in the inner ear and other organs: electrophoretic microanalysis

Selective urinary screening for mucopolysaccharidoses

Two methods for analysis of urinary glycosaminoglycans (GAGs) have been modified and improved for efficient screening of mucopolysaccharidoses. Urinary excretion of GAGs was estimated by spectrophometric measurement of alcian blue complex formation and was used in conjunction with qualitative analysis by thin layer chromatography. After normal variation in GAG excretion was established using 120 urine samples, these screening methods were applied to a total of 2057 urine samples over 4 years. Six patients with abnormal urinary GAG excretion had a mean of 50.5 +/- 20.6 mg GAG/mmol creatinine compared to 3.4 +/- 2.9 for age-matched controls. Qualitative analysis by thin layer chromatography using alternating solvent systems identified the GAGs excreted in excess and facilitated selection of specific enzyme assays for final confirmation. Six cases were diagnosed prospectively and demonstrate these quantitative and qualitative methods to be economical, efficient, and suitable for clinical use.

Morphologic study of effects of kanamycin on the developing cochlea of the rat

The development of the rat inner ear starts about day 9 of a 22-day gestational period. The sensory and supporting cells are morphologically identifiable by day 18 of gestation; however, auditory function is not evident until day 9 postnatally. The organ of Corti attains adult maturity about day 16 postnatally. Morphologic and physiologic studies have shown that administration of sublethal doses of aminoglycosidic antibiotics, including kanamycin, damages the sensory and supporting cells of the inner ear in mammals. This results in the impairment of auditory function. This study was designed to determine the earliest stage in cochlear duct development at which kanamycin toxicity can be morphologically detected. A sublethal dose of kanamycin was administered to pregnant rats on days 10 through 20 of gestation and to neonates from days 1 to 8 or from days 8 to 16 postnatally. The inner ears were dissected and processed for light microscopic and ultrastructural observations. The cochlear ducts of fetuses exposed in utero to kanamycin and those of neonates exposed from days to 1 to 8 postnatally were unaffected. Kanamycin toxicity was evident in the cochlear ducts of neonates exposed from days 8 to 16 postnatally. The most severe damage occurred in the basal coil of the cochlea where in many instances sensory cells were totally absent. The sensory cells in the middle and apical coils exhibited abnormal morphology. These results suggest: (1) kanamycin does not have any permanent toxic effects on the rat cochlear duct during gestation and the first week of postnatal life. This provides a basis for further studies into the possible pharmacologic application of this finding in humans. (2) A correlation exists between the initiation of auditory function and the vulnerability of the organ of Corti to kanamycin toxicity.

A possible involvement of acidic glycosaminoglycans in kanamycin ototoxicity

The content of acidic glycosaminoglycans (AGAG) was determined quantitatively by electrophoretic microanalysis in the cochlea, kidney and brain of the guinea pig. Kanamycin treatment (400 mg/kg body weight/day, i.m., 10 successive days) reduced the content of AGAG markedly in the lateral wall of the membranous cochlea. Furthermore, from the results of the ultrahistochemical and freeze-fracturing study, we propose here an "excretion system for basic aminoglycoside antibiotics" by means of the co-operation of spiral ligament cells and AGAG produced by them. Thus we have tentatively concluded both that kanamycin is excreted via the above mentioned "excretion system" in the lateral wall of the membranous cochlea and that it damages this system to form the circulus vitiosus of its opopoxicity.

Tissue levels of kanamycin in correlation with oto- and nephrotoxicity

The time courses of kanamycin (KM) levels in the perilymph, kidney, liver, brain and blood were observed by a bioassay method in normal guinea pigs and in animals pretreated with KM for 10 successive days. In the kidney and perilymph of the normal guinea pigs, the injected KM became highly concentrated and was eliminated only after a protracted delay. This tendency was much more intensified in kidney and perilymph of the pretreated animals. By contrast, the KM in blood and brain was eliminated rapidly both in the normal and in the pretreated animals. It is concluded that the high accumulation and slow elimination of KM by the inner ear and kidney and, moreover, the enhancement of these phenomena by successive pretreatment are one of the important factors in the origin of oto- and nephrotoxicity.