Acid Phosphatase Activity in the Inner Ear

Abstract

Frozen sections of fetal and adult guinea pig inner ears were studied for acid phosphatase activity, utilizing naphthol AS-BI phosphate as substrate and hexazonium pararosanilin as a coupler. Azo dye deposits indicating the sites of enzyme activity were observed in various cell types. In the outer hair cells, enzyme activity was limited to the subcuticular area which is known to contain lysosomes and lipofuscin, thus suggesting a possible relation between acid phosphatase activity and the accumulation of insoluble metabolic end-products. Supranuclear distribution of enzyme activity characterized the inner hair cells and vestibular sensory epithelium. Other sites of considerable acid phosphatase activity included the stria vascularis, outer sulcus cells and limbus cells in the cochlea, as well as the dark cells at the base of the crista ampullaris. The ganglion cells of the spiral and vestibular ganglion also revealed marked to moderate acid phosphatase activity.