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Journal of Dairy Science Vol. 54 No. 7 1068-1074
© 1971 by American Dairy Science Association ®
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Nucleic Acid and Collagen Content of Mammary Glands Between 30 and 80 Days of Age in Normal and Ovariectomized Rats and During Pregnancy

M. J. Paape and Y. N. Sinha1

Animal Science Research Division, ARS, USDA, Beltsville, Maryland 20705
Department of Animal Science, Cornell University, Ithaca, New York 14850

ABSTRACT

Nucleic acid and collagen content of parenchymal and extraparenchymal fat pad portions of mammary glands were determined at 10-day intervals from 30 to 80 days of age in ovariectomized, sharnovariectomized, and intact rats; and at 6-day intervals throughout pregnancy. Pubertal development of the mammary gland was characterized not only by an increase of cell numbers (desoxyribonucleic acid) but also by 8. substantial increase in connective tissue elements (collagen) which was shared both by parenchymal and fat pad segments of the mammary gland. Ovariectomy reduced (P < 0.01) epithelial cell numbers (DNA), protein synthesis (ribonucleic acid), and to a lesser extent collagen in the mammary gland parenchyma but produced (P < 0.01) net increases of these constituents in the mammary fat pad, suggesting that factors other than ovarian steroids also play an important role in collagen synthesis by the mammary gland.

On the other hand, during pregnancy, mammary growth was reflected only in the parenchymal portion and occurred at the cost of fat pad although, contrary to the earlier view, collagen continued to increase throughout pregnancy. The major part of the collagenous framework of the mammary parenchyma, however, was formed prior to major epithelial cell growth, suggesting that the collagenous framework of the gland may be necessary for epithelial cell growth.

FOOTNOTES

1 Present address: Division of Endocrinology, Scripps Clinic and Research Foundation, La Jolla, California 92037.






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Copyright © 1971 by the American Dairy Science Association ®.