SEQUENTIAL CHANGES OF LACTATE DEHYDROGENASE AND ITS ISOENZYMES IN METHYLCHOLANTHRENE BRAIN TUMOURS OF WISTAR ALBINO RAT

Sequential changes of LDH and its isoenzymes in the serum and brain tissue of 340 control and 340 test Wistar rats maintained at the Animal Experimental Laboratory, Madras Medical College, were studied using 20 MCA as carcinogen. The mean values, total LDH of serum and brain of the control animals showed no statistically significant change between sexes. From 150 days till 720 days the rise in the values of the serum and brain tissue of the test males were statistically significant (P <0.001). In test females a similar rise was seen from 300 days. Five isoenzymes namely LDH₁, LDH₂, LDH₃, LDH₄ and LDH₅ were detected in the control serum of both sexes throughout the study. The isoenzymes from LDH₁ to LDH₄, gradually decreased from 30 days to 720 days in test animals. While LDH₅ was prominently seen from the initial period to the end of the period. In both sexes of control animals the brain tissue showed all the five isoenzymes. In contrast to the serum, the LDH₅ was not seen in the brain tissue of the test animals. A preband was seen before the LDH₁ fraction in test males and females on 300, 330 and 360 days and disappeared from 390 days onwards till 720 days. In the present work, statistically significant fall in the H/M ratio was observed in serum and tissue samples of the 180 days male test animals. The lowest value was recorded on 300 days whereas in the test females the fall begins at 300 days and the maximum depression is on 450 days of both serum and tissue samples.