Phylogenetic relationships of rodents on the basis of isoenzymes of lactate dehydrogenase

1. 1. The isoenzymes of lactate dehydrogenase (LDH) were compared in twenty-two rodents. 2. 2. LDH 1 of three electrophoretic mobilities and LDH 5 of four mobilities were found. 3. 3. Erythrocytes of the more primitive classes contained several LDH isoenzymes whereas in most of the Cricetidae and Muridae only LDH 5 was found. 4. 4. In the kidney the distribution of LDH isoenzymes also varied widely. 5. 5. In the heart, liver and skeletal muscle no prominent differences were observed. 6. 6. Meriones unguiculatus (Mongolian gerbil) was found to have a sixth LDH isoenzyme in both kidney and heart. 7. 7. The evolutionary development and genetic control of isoenzyme patterns is discussed.