GTTR fluorescence in the 21−28 day old murine cochleae examined at 3 (A, D), 24 (B) and 72 h (C) after GT/GTTR injection. (A) Weak, diffuse GTTR fluorescence in hair cells and pillar cells (PC) 3 h post-injection. (B) Both diffuse and punctate GTTR fluorescence are present in IHCs and OHCs hair cells 24 h post-injection. (C) Punctate and diffuse GTTR fluorescence in the organ of Corti (after 3 daily injections of GT/GTTR), 72 h after the initial injection. OHCs have greater intensity of GTTR fluorescence than IHCs. (D) Three hours after GT/GTTR injection, and 2 h after ethacrynic acid injection, increased diffuse GTTR fluorescence occurred in OHCs compared to OHCs from animals treated without ethacrynic acid (A, B, C). All images acquired and post-processed identically. Scale bar applies to all images.