Decreased adenosine triphosphatase activity in the absence of adrenocorticosteroids.

Changes in adenosine triphosphatase activity and cellular integrity of rat inner-ear tissues were observed after removal of adrenal steroids via bilateral adrenalectomy. Statistical significance of total and magnesium ion-dependent adenosine triphosphatase activities of the stria vascularis, spiral ligament, and ampullar dark cells from adrenalectomized animals was detected when compared with those of controls as demonstrated by fluorometric microassay. Although there was a similar reduction of activity in utricular dark-cell tissues, no significant difference between the treated and control animals was observed. An increase of intercellular space and a decrease in basolateral infoldings of cells of the stria vascularis and dark cell regions of adrenalectomized animals were observed. Such data collectively provide indirect evidence that adrenal steroids are involved in the cellular regulation of inner-ear tissues that are concerned with fluid and ionic microhomeostasis.