Age- and Strain-Related Differences in Dehydrogenase Activity and Glycogen Levels in CBA and C57 Mouse Cochleas

Abstract

In the C57 mouse strain, loss of sensory hair cells (HCs) begins during early adulthood, starting in the base of the cochlea and progressing toward the apex as aging continues. In contrast, the CBA mouse strain exhibits no significant cochlear histopathology until relatively late in life. These strain and age differences may be related to differences in cochlear energy metabolism. To examine this possibility, we used dehydrogenase and glycogen histochemistry to evaluate the metabolic capacities of HCs and stria vascularis (SV) in cochleas of C57 and CBA mice. Reaction product density was quantified and compared as a function of strain (1.5-month-old C57 mice vs. CBA mice) and age (CBA mice, 1.5, 18 and 36 months). Young C57 mice had significantly less HC dehydrogenase activity than CBA mice of any age, lower HC glycogen levels than 18-month-old CBA mice and lower SV glycogen levels than 18- or 36-month-old CBA animals. Within the CBA strain, HC dehydrogenase activity decreased significantly between 1.5 and 18 months of age, while glycogen levels in both HCs and SV increased over the same time period. Between 18 and 36 months, HC dehydrogenase activity and SV glycogen levels remained stable. The results show that there are significant age-related changes in energy metabolism in the inner ear of CBA mice that are correlated with age-related hearing loss. Genetically determined deficits in cochlear metabolic capacity in C57 mice could be linked to the early onset of hearing loss in this strain.

<i>D</i>-Methionine Attenuates Inner Hair Cell Loss in Carboplatin-Treated Chinchillas

“…The bullae were quickly removed and opened to expose the cochleae. The round window, oval window, and apex of the cochleae were opened and the cochleae perfused with a succinate dehydrogenase staining solution (2.5 ml of 0.2 M sodium succinate, 2.5 ml of 0.2 M phosphate buffer, pH 7.6 and 5 ml of a 0.1% nitroblue tetrazolium solution) [Ding et al, 1999]. The cochleae were immersed in the staining solution at 37°C for 45 min.…”

Modulation of Presbycusis: Current Status and Future Directions

“…The treated rats had better cochlear function than control rats that were fed a placebo. In another study on rodents, Ding et al [1999] found evidence that age-related changes in the inner ear of CBA mice were correlated with altered energy metabolism. Whereas a good deal more research needs to be done, the data indicate that some forms of presbycusis are associated with mitochondrial dysfunction in cochlear cells and suggest new therapeutic directions aimed at mitochondrial health [see also Fischel-Ghodsian, 1999;Seidman et al, 1996a.…”

Overexpression of X-linked inhibitor of apoptosis protein protects against noise-induced hearing loss in mice

“…72,73 After the final ABR test, the mice were deeply anaesthetized with an overdose of ketamine, and the cochleae rapidly harvested. Surrounding soft tissues were removed and the round window and oval window were both opened.…”