In vitro and in vivo study of glutamate dehydrogenase encapsulated into mouse erythrocytes by a hypotonic dialysis procedure

Glutamate dehydrogenase (GDH) has been encapsulated into mouse erythrocytes by a hypotonic dialysis/isotonic resealing method. Although a low GDH entr apment yield was achieved (3.8%), this percentage appeared sufficient enoug h to metabolize high quantities of ammonia. Carrier cell recovery yield was 56%. Due to the decrease in cell volume and haemoglobin content, constant mean cell haemoglobin concentration (MCHC) values were obtained. The osmoti c fragility curves (OFC) indicated that dialyzed/resealed-RBCs are more res istant to hypotonic haemolysis than native-RBCs. The successful in vitro am monia degradation by GDH-RBCs was reflected in its total disappearance from the incubation medium at around 48 h. In contrast, initial ammonia levels were not affected during the incubation in the presence of native-RBCs and remained constant. Two different methods were used for the preparation of h yperammonaemic mice model. Since the intraperitoneal (i.p.) administration of ammonium acetate produced high ammonia levels that lasted only a few min utes, the i.p. administration of urease was chosen, given that it generated elevated ammonia levels for longer periods of time. Hyperammonaemic mice q uickly removed high levels of circulating ammonia in the presence of GDH-RB Cs, whereas in the presence of native-RBCs ammonia was slowly metabolized. These results suggest that loaded GDH-erythrocytes can be used as a potenti al carrier systems for the in vivo removal of high levels of ammonia from b lood.