Provided are uses of selective aquaporin inhibitors, e.g., of aquaporin-4 or aquaporin-2, e.g., certain phenylbenzamide compounds, for the treatment or prophylaxis of transplant rejection and the protection of the heart during heart surgery. Provided is the use of selective aquaporin inhibitors, e.g., of aquaporin-4 (AQP4) or aquaporin-2 (AQP2) for the treatment or prophylaxis of transplant rejection and for the protection of the heart during heart surgery.