Abstract
Summary
Virgin ovariectomized rats were primed with a combination of estradiol and progesterone (EP) for 20 days to promote mammary gland development similar to that of normal pregnancy. EP injections were discontinued at Day 20 and we attempted to induce an experimental lactational mammary gland growth by giving cor-tisol (C), prolactin (L), and growth hormone (G), alone and in combination, for the next 3 days. The group treated with C alone exhibited the greatest degree of lactational activity with significant elevations in DNA, RNA, and nitrogen content of the mammary glands. If EP was administered simultaneously with C, G, and L, all hor-monally induced increases in DNA, RNA, and nitrogen were inhibited. The results were interpreted as indicating that levels of EP during normal pregnancy not only hold milk secretion in abeyance until parturition, but also block the particular type of mitotic growth phase associated with early lactation in the rat.
Get full access to this article
View all access options for this article.