ALTERED CALCIUM HOMEOSTASIS IN THE RAT COCHLEAR DUCT AND ENDOGENOUS CORTICOSTEROID INSUFFICIENCY

Free calcium concentration (C-Ca(2+)) profiles were evaluated in peril ymph, endolymph, marginal cells, spiral ligament and blood serum of ad renalectomized (ADX) rats. Free C-Ca(2+) was significantly greater in perilymph and significantly reduced in the serum of the ADX animals as compared to sham-operated animals. In addition, higher levels of free C-Ca(2+) were found in the spiral ligament in ADX animals. Free C-Ca( 2+) did not appear to be affected by ADX in marginal cells and endolym ph. These data suggest that marked reductions in endogenous levels of corticosteroids may have a systematic effect on free C-Ca(2+) that is detectable in blood serum as well as cochlear fluids and tissues.