Changes in morphology and in the amount of nucleic acids in mammary glands of pregnant and lactating ddY mice
2001
Uechi, S. (Ryukyu Univ., Nishihara, Okinawa (Japan). Coll. of Agriculture) | Mori, K. | Oizumi, H. | Simizu, M. | Yogi, S. | Nakada, T. | Hongo, F.
Primiparous ddY mice were used to determine the extent of mammary gland growth during pregnancy and lactation. Mice were autopsied at day 0, 5, 10 and 15 of pregnancy, and day 7 of lactation. Mammary glands (third thoracic mammary) were collected from the skin at the thoracic region following the removal of skin fat. The weight of the dry fat-free mammary gland, mammary gland area, deoxyribonucleic acid (DNA) content, and ribonucleic acid (RNA) content were measured. 1. Mammary gland weight increased gradually with the progress of pregnancy. The maximum weight was observed at the lactating phase. The area of mammary gland tissue also aligned with the weight of the mammary gland, and it showed maximum value at the lactating phase. In morphology, it was found that the basic structure of the mammary gland changed in connection with progress of pregnancy, during the lactation phase, and then the round alveolar cells came to cover the whole mammary gland tissue. 2. The total amount of DNA and RNA in the mammary glands increased linearly after the 10th day of the pregnancy, and each showed maximum growth on the 7th day of lactation. Except for the value of day 5 of pregnancy, the RNA/DNA ratio also increased linearly in connection with progress of pregnancy, and showed maximum growth during the lactating phase. From these results it is concluded that progressive changes in both morphology and nucleic acid contents in the mammary glands of pregnant and lactating ddY mice could be investigated.
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