Effect of zinc ion on cadmium-induced auditory changes.
ABSTRACT Cadmium, which has adverse effects on many physiological systems, is an important environmental pollutant. Our previous experimental study showed that cadmium also has a dose-dependent deleterious effect on the auditory system in rats. Because zinc reverses cadmium cytotoxicity in many systems, we investigated the possible preventive effect of a zinc-enriched diet given isochronally on cadmium-induced hearing loss in rats. Fifty-four male rats were divided into three equal groups. Control rats were fed normal rat food and tap water, whereas the cadmium group was subjected to 15 ppm cadmium-containing water as CdCl2. The third group received 15 ppm CdCl2 and food enriched with 200 ppm zinc as ZnSO4 for 30 d. On d 30, eight animals from each group were used for the measurement of kidney functions. In the remaining animals, hearing functions were measured by auditory brainstem response and distortion product otoacoustic emission. Blood cadmium increased from 1.87+/-1.69 to 6.08+/-2.62 microg/dL and elevated cadmium contents of ear ossicles and kidney cortex were associated with a decreased glomerular filtration rate in rats subjected to high cadmium. A zinc-enriched diet obviously reduced cadmium accumulation in the kidney and prevented the nephrotoxicity. Our data indicated that cadmium-induced ototoxicity seems to be partially zinc preventable and zinc addition to diet without altering cadmium content in ear ossicles may help to prevent cadmium-induced hearing loss.
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ABSTRACT: Previous studies have shown that environmentally significant concentrations (< 1 microM) of large divalent cations increased vascular tone in resistance arteries. Because K channels are important regulators of vasoactivity, we studied the interactions of Cd and Ni on K channels of smooth muscle from bovine mesenteric artery using the planar bilayer method. We describe one type of small, Ca-insensitive K channel (Ks), and two types of large, Ca-activated K channels ([BK(Ca)], Kc1 and Kc2, that were identical with respect to single-channel conductance and K/Cl selectivity, but differed in Ca/voltage sensitivity. Neither metal affected the open probability (po) of Ks but both Cd and Ni, in concentrations greater than or equal to 100 nM, similarly decreased po of Kc1 and Kc2 from the intracellular side of the channel in the presence of 1 microM Ca. The effects of both Cd and Ni were reversed by 0.1 mM Ca. It is concluded that Cd and Ni, in concentrations less than 1 microM, can interact with the Ca/voltage sensor and inhibit BK(Ca) channels of vascular smooth muscle. These effects may partially explain the vascular tension induced by large divalent cations.Toxicology and Applied Pharmacology 07/1993; 121(1):30-5. · 3.98 Impact Factor
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ABSTRACT: The structural features of the basal lamina in Reissner's membrane were examined electron microscopically using tannic acid fixation, poly-cationic staining (ruthenium red), and mono-cationic staining (safranin O). Tannic acid fixation revealed 5-10-nm filaments which ran perpendicularly between the lamina densa and the cytoplasmic surface of squamous epithelial cells. Ruthenium red staining showed a lattice-like arrangement of anionic sites on both sides of the lamina densa. Safranin O staining revealed filamentous networks at the same sites. These structural features of the basal lamina in the Reissner's membrane were very similar to those of the glomerular and the alveolar basement membrane. Therefore, the possibility that anionic sites of Reissner's membrane may play the role of a size and charge-selective barrier between the scala media and the scala vestibuli, in much the same way that the glomerular basement membrane plays the same role of barrier, must be taken into account.Acta Oto-Laryngologica 01/1985; 100(3-4):194-200. · 1.11 Impact Factor
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ABSTRACT: Brainstem auditory evoked responses of 355 patients with uni- or bilateral tinnitus were recorded in order to evaluate the effect of tinnitus on the central auditory system. The amplitudes of waves I, III and V and the latencies of each wave and interpeak latencies were compared to those of a group of 129 controls with normal hearing. The study of the control group initially identified a certain number of concurrent parameters. The brainstem evoked responses of men and women evolved differently from the age of 30 years, latencies of I-III and I-V in men lengthening with age and those of women tending to shorten. The patient groups were therefore compared to a control group of the same sex ratio or of the same sex, half being between 30 and 56 years of age. The tinnitus patients were divided into three groups according to the side affected by tinnitus. Latencies and amplitudes in these groups differed significantly from those of the control group. In order to eliminate hearing loss, the most difficult concurrent factor and almost always associated with tinnitus, the results of individuals with symmetrical hearing loss were compared to those of the control group. Tinnitus was always associated with significant lengthening of 0-I and I-V latencies on the tinnitus-affected side, with a significant reduction in amplitudes of waves I and III, and sometimes of wave V, particularly in the group with left-sided tinnitus. Comparison of tinnitus patients with symmetrical and asymmetrical hearing by sex showed that tinnitus patients of all groups had lengthening of right and left 0-I latencies, apart from the women in the group with right-sided tinnitus, and significant reduction in amplitudes of waves I and III in women and of left III only in men. When hearing loss was asymmetrical and on the tinnitus-affected side, there was also lengthening of 0-I latencies on the tinnitus-affected side in both sexes and of ipsi- and contralateral I-V latencies in women. Right- and left-sided tinnitus was associated with additional differences between the three groups. Correlation coefficient study confirmed that 0-I, I- III and I-V latencies were independent of the mean degree of deafness, deafness at high frequencies and at frequencies around the tinnitus, up to a threshold of hearing loss of 40 dB, above which 0-I and 0-V lengthened in addition to tinnitus. On the other hand, whatever the frequency, tinnitus involved significant lengthening of wave I latencies and modification of the previously recorded amplitudes. Two groups of tinnitus patients could be distinguished: the first, with symmetrical hearing loss, with symmetrical normal latencies, apart from 0-I latencies and the amplitude of the wave on the tinnitus side, and the second with hearing loss predominant on the tinnitus-affected side, with different latencies on each side, 0-I being shorter on the unaffected side, I-III and I-V being lengthened on the unaffected side and 0-I being lengthened on the tinnitus-affected side. Moreover, as disturbances of brainstem evoked responses caused by tinnitus particularly affected waves I and III, the hypothesis of possible involvement of the efferent systems could be proposed.Audiology: official organ of the International Society of Audiology 01/1995; 34(6):287-300.