Rabbit Endometrial RNA- and DNA-Dependent DNA Polymerase Activity

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Abstract
Changes in rabbit endometrial RNA- and DNA-dependent DNA polymerase activity were studied during the 1st 9 days of pregnancy. Both enzyme activities are low at estrus and 1 day postcoitum, but measurable increases in activity occur by 48 h after coitus. The RNA-dependent DNA polymerase (RDDP) activity reaches a maximum on Days 3-4 postcoitum, a level it maintains except for slight drops on Days 5 and 8-9. The DNA-dependent DNA polymerase (DDDP) activity initiates a rise on Day 1 postcoitum, to reach a peak on Day 6 and remains at this level through Day 8, but drops significantly on Day 9. When polymerase levels are obtained for pseudopregnant animals, the RDDP activity parallels that of pregnant animals up to Day 5 and the DDDP activity attains levels comparable to Day 6 pregnancy levels. In pseudopregnancy, RDDP activity drops precipitously on Day 6 resuming its usual high level again on Day 8, while DDDP activity remains high through Day 6, dropping on Day 8 of pregnancy. Low levels of both RNA-dependent and DNA-dependent DNA polymerase activity can be induced by either estrogen or progesterone administration to ovariectomized does. However, the high levels of enzyme activity normally found in Days 3-4 of pregnancy can only be induced through the synergistic effects of estrogen and progesterone.