Peroxidase activity (PA) and progesterone receptors (PgR) in normal rat mammary glands.

PA and PgR appear to be reliable markers of estradiol action in normal female rat mammary glands, as seen by simultaneous expression of both proteins between the ages of 61 and 131 days. However, expression of PA at certain periods, when PgR was undetectable suggests, that the extent of availability of both estradiol and progesterone at target sites may act as controlling factors in synthesis of one protein over another.