Total lactate dehydrogenase-specific activity and concentration of isoenzymes were determined on extracts of rat uterus at different stages of pregnancy, during the oestrous cycle and after ovariectomy.
Total enzymatic activity increased during pregnancy. The rise was evident by the 5th day and continued steadily until the 14th day, when it attained maximal values. These high values were maintained up to the end of pregnancy and fell to the level of controls 4 days after parturition.
The changes in enzyme activity were entirely due to variations in the amount of Isoenzymes 5 (A4) and 4 (A3B1). The other three molecular forms were not modified
Total specific activity and Isoenzymes 5 and 4 were diminished 20 days after ovariectomy.