Meg asks: << Can someone explain how lactose synthesis affects the secretion
of water into milk and hence milk production? >>

Here's a simplified explanation: The glandular secretory cells in the
alveoli start making proteins and fat during pregnancy, which we call
colostrum. High levels of serum progesterone from the placenta "keep the lid
on" the high levels of serum prolactin normally present during pregnancy.
When the placenta delivers, progesterone is suddenly withdrawn and prolactin
can act unopposed. This  triggers lactose synthesis in the secretory cells.
As the fluid (protein + fat) secreted starts getting sweeter, the osmolar
pressure becomes higher, which draws fluid from the surrounding tissue via
osmosis. (Like when you eat something sweet, you get thirsty pretty quick.)
The fluid secreted is now protein + fat + lactose + water = mature milk.
(OK, I know this is oversimplified and that milk is much more complex.)
Meg, this is a great question for Lactnet.  Keep 'em coming.

Linda J. Smith, BSE, FACCE, IBCLC
Bright Future Lactation Resource Centre www.bflrc.com
6540 Cedarview Ct., Dayton, OH 45459-1214 USA
(937) 438-9458 email [log in to unmask]

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