Early effects of ethacrynic acid on cochlear histochemistry

We have investigated the histochemical changes in the succinodehydrogenase (SDH) and adenosine triphosphatase (ATPase) enzyme systems of the guinea pig cochlea at 30, 60, and 240 minutes following the intracardiac injection of ethacrynic acid. In control animals, there is intense SDH activity in the stria vascularis, spiral prominence, and hair cells. At all periods after ethacrynic acid injection, there was decreased activity of SDH in the outer hair cells in the basal turn. The activity of SDH in the stria vascularis and spiral prominence was equally as intense as in control animals at all periods, however. Strong ATPase activity in control animals was demonstrated by dark-brown precipitations in the external sulcus cells, stria vascularis, and hair cells. The ATPase activity was decreased at 60 minutes after ethacrynic acid injection only in the stria vascularis. The importance of these results is discussed.