Milk yield in rats in relation to activity and size of the mammary secretory cell population

An attempt was made to partition changes in milk yield during lactation in the rat between changes in the size of the secretory cell population and changes in cellular activity. Groups of rats were studied on d 2, 7, 14, 21 and 28 of lactation. Milk yield increased between d 2 and 7, less markedly between d 7 and 14 and decreased between d 14 and 21. Milk secretion had apparently ceased on d 28. Total mammary DNA (DNAt) and RNA (RNAt) increased from d 2 to 14. It is concluded that of the increase in milk yield between d 2 and 14, an increase in cell population accounted for 75% and an increase in cellular activity for 25%. A decrease in activity appeared to be entirely responsible for the decrease in yield between d 14 and 21.

[1]  H. Tucker.  Regulation of mammary nucleic acid content by various suckling intensities. , 1966, The American journal of physiology.

[2]  D. R. Griffith,et al.  Normal Growth of Rat Mammary Glands During Pregnancy and Early Lactation.∗ , 1959, Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine.

[3]  C. Knight,et al.  Development of the mammary gland. , 1982, Journal of reproduction and fertility.

[4]  B. Mackay,et al.  Plasma prolactin levels and body fluid deficits in the rat: causal interactions and control of water intake. , 1983, The Journal of physiology.

[5]  C. Pollard,et al.  Water balance of small lactating rodents--II. Concentration and composition of milk of females on ad libitum and restricted water intakes. , 1976, Comparative biochemistry and physiology. A, Comparative physiology.

[6]  J. Linzell,et al.  A simple technique for measuring the rate of milk secretion in the rat. , 1972, Comparative biochemistry and physiology. A, Comparative physiology.

[7]  C. Knight,et al.  Mammary cell proliferation in mice during pregnancy and lactation in relation to milk yield. , 1982, Quarterly journal of experimental physiology.

[8]  J. Linzell,et al.  The effects of engorgement with milk and of suckling on mammary blood flow in the rat , 1973, The Journal of physiology.

[9]  C. Knight,et al.  Mammary development in mice: effects of hemihysterectomy in pregnancy and of litter size post partum , 1982, The Journal of physiology.