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

Abstract

Glutamate dehydrogenase (GDH) has been encapsulated into mouse erythrocytes by a hypotonic dialysis/isotonic resealing method. Although a low GDH entrapment yield was achieved (3.8%), this percentage appeared sufficient enough 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 osmotic fragility curves (OFC) indicated that dialyzed/resealed-RBCs are more resistant to hypotonic haemolysis than native-RBCs. The successful in vitro ammonia 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 hyperammonaemic mice model. Since the intraperitoneal (i.p.) administration of ammonium acetate produced high ammonia levels that lasted only a few minutes, the i.p. administration of urease was chosen, given that it generated elevated ammonia levels for longer periods of time. Hyperammonaemic mice quickly removed high levels of circulating ammonia in the presence of GDH-RBCs, whereas in the presence of native-RBCs ammonia was slowly metabolized. These results suggest that loaded GDH-erythrocytes can be used as a potential carrier systems for the in vivo removal of high levels of ammonia from blood.