EFFECTS OF PHOTODEGRADATION OF NIFEDIPINE ON DOG ERYTHROCYTE-MEMBRANES

studied the effects of nifedipine (NF) on UV-induced photohemolysis of erythrocytes in vitro. A suspension in physiologic saline of erythroc ytes separated from the venous blood sample freshly obtained from a do g was prepared and used.NF is a photolabile agent, and this drug was e xtremely sensitive to the long wavelength (365 nm) of UV light. The mo st abundant photodegradation product was a nitroso-derivative which ch anged into a lactam-derivative in the dog erythrocyte suspension with or without irradiation. NF itself showed protective effects against ph otohemolysis of erythrocytes caused by 365 nm of UV light as well as h ypotonic hemolysis. But NF enhanced the degree of photohemolysis under oxygen condition. The photohemolysis enhanced by NF was reduced by th iobarbituric acid, indicating an oxidative stress by a radical interme diate of NF to photohemolysis. Ori-the other hand, the nitroso-derivat ive reacted with erythrocyte hemoglobin spectroscopically to change in to the lactam-derivative. It is considered that NF is a phototoxic age nt to cause photohemolysis by producing a radical intermediate with ox ygen and unknown species of hemoglobin degraded with the nitroso-deriv ative of nifedipine photoproduct.