Lysyl oxidase activity in the mouse uterine cervix is physiologically regulated by estrogen

Lysyl oxidase activity in the mouse cervix was examined during the estrous cycle, pregnancy, and the postpartum period. It was highest in estrus and lowest in diestrus. On day 1 of pregnancy, the activity was comparable to that seen in estrus. It then declined continuously until day 17 of pregnancy, when it was approximately equal to that seen during diestrus. The activity showed a slight increase toward term, then a precipitous increase occurred on the first postpartum day. The activity fell by the seventh postpartum day to a value comparable to that seen in diestrus. Enzyme activity fell to one fourth of its former value 3 days after ovariectomy. The injection of 1 microgram 17 beta-estradiol or more in 0.9% NaCl 10 days after ovariectomy raised the activity, in 18 h, to the level seen in estrus. One milligram of progesterone had no effect on the enzyme activity, but a combination of 1 microgram 17 beta-estradiol and 1 mg progesterone raised the activity to that seen with 1 microgram 17 beta-estradiol alone. These results suggest that lysyl oxidase activity in the mouse cervix is under the control of estrogen.