Rat endometrium enzymes in 4-day oestrous cycle and early pregnancy.

The specific activities of lactate dehydrogenase (LDH) and its M-type (M-LDH), beta-glucuronidase (beta-GR), acid phosphatase (ACP) and alkaline phosphatase (AP) were determined. The specific activities of the enzymes (LDH, beta-GR) in the myometrium were lower and their changes less pronounced than in the endometrium. We, therefore, determined the enzymes in the rat endometrium only in further experiments. All enzymes react sensitively to the changes induced in the endometrium by endogenous hormones in the course of a 4-day cycle: pro-oestrus (P) is characterized by rather low enzyme activities, oestrus (E) by a peak of LDH and M-LDH and a rise of AP. In metoestrus (M) there is a peak of beta-GR, ACP and AP. Dioestrus (D) is characterized by a significant decrease in LDH and M-LDH and by elevated values of all the other enzymes. The values on the individual days of the 4-day cycle were compared with days 4-6 of pregnancy. The reason for this was that if the rats were not mated, they would, respectively, return to pro-oestrus instead of being 4 days pregnant, to oestrus instead of being 5 days pregnant, or to metoestrus instead of being 6 days pregnant. We found the following differences: on day 4 of pregnancy LDH and M-LDH were lower and ACP and AP higher than in P. On day 5 of pregnancy the LDH, M-LDH, beta-GR and AP were lower than in E. On day 6 of pregnancy the LDH, M-LDH, ACP and especially beta-GR, were lower than in M.