The prolactin receptors are on the milk gland cells that make up the
alveolar ascini.  More receptors allows more prolactin to get into the
cell at one time (like having more doors for the workers to enter the
factory, allows them to get in and get to work faster than if they have
to line up single file and wait their turn).  Prolactin catalyzes the
formation of lactose and alpha-lactalbumin, the main protein in human
milk, and feeds into the pathway that produces the fats in milk as well,
all three macronutrient groups with one hormone, how elegant!  The more
prolactin that can enter the cell at once, the more milk constituents
can be made per unit of time, up to the rate limiting factor of the
lowest concentration raw material.
        A similar discussion occured on lactnet a few years ago, should be in
the archives, perhaps under mechanism of milk production.
--
Catherine Watson Genna, IBCLC  New York City  mailto:[log in to unmask]

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