Incorporation Of Radioactive Calcium Into Otolithic Membranes And Middle Ear Ossicles Of The Gerbil

Abstract

⁴⁵CaCl₂ was injected into gerbils in single or multiple doses, and the resulting radioactivity in serum, otoconial CaCO₃, bone samples, and selected labyrinthine epithelium was determined by liquid scintillation spectrometry. Incorporation into both utricularand saccu-lar otoconia occurred at the rate of 0.06–0.07 nmole Ca⁺⁺ per day, corresponding to a fractional rate of uptake of 0.1%. The retention of radioactivity had a half-life of approximately 11 days. The rate of incorporation of calcium for the middle ear ossicles was 5–7 times that for otoconia and was similar to that for otic capsule and skeletal bone. The level of ⁴⁵Ca⁺⁺ was higher in the pigmented regions of the utricular membranous wall than in the non-pigmented areas of the utricular and ampullary wall and in the stria vascularis.