Growth Autoregulation and the Mammary Gland2

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Abstract
The possibility that the rate of mammary duct growth is controlled by a systemically operating self-regulatory mechanism was investigated with the use of C3H/Crgl or C3H/Crgl/2 mice. Three-week-old females were subtotally mastectomized (only the right #2 and 3 glands left intact), and the growth rate of the ducts of the #2 gland was compared with that of sham-operated and intact controls. No differences were found either at 1 or 3 weeks after surgery. No difference was found, after 3 weeks of growth, in duct length of mammary glands grown from a transplant of primary duct in cleared #4 fat pads of estrogen-treated mice that were either totally mastectomized or had received transplants of 10 additional mammary glands (polymastic). Subtotal mastectomy of nonpregnant, multiparous mice did not result in a difference in the degree of lobuloalveolar development in the remaining right #2 and 3 mammary glands when compared with sham-operated controls 6 weeks after surgery. Injections of mammary tissue extract three times a day for 5 days did not influence mammary duct growth of 3-week-old females, though an equivalent quantity of combined kidney, liver, and spleen extract did depress duct growth. These experiments provide no evidence for a humoral factor responsible for autoregulation of mammary duct growth.