Tinoridine hydrochloride (Y-3642 hydrochloride) is a non-steroidal anti-inflammatory drug. Tinoridine hydrochloride (5-100 μM), produced a concentration-dependent inhibition on the simultaneous increases in lipid peroxide formation and renin release induced by 50 μM ascorbic acid in the renin granule fraction. On the other hand, indomethacin, hydrocortisone, and prednisolone, which had no ability to inhibit the lipid peroxidation in the renin granule fraction, did not influence the release of renin from the granules. These results suggest that tinoridine suppresses renin release by inhibiting the oxidative disintegration of membranes of renin granules.