On 5/9/02 9:03 PM, "Automatic digest processor"
<[log in to unmask]> wrote:

> I understand the differentiation between serum prolactin and milk prolactin
> .. but where does milk prolactin come from if not originally from the
> maternal blood stream?  High levels of serum prolactin may not influence
> milk production at all, but surely low levels of serum prolactin result in
> low levels of milk prolactin and hence reduced milk production (ie overall
> output, not rate of synthesis).
>
> I continue to pursue this topic in an effort to understand the role of
> galactagogues.  Prof Hartmann has suggested that before we give
> galactagogues we should check serum prolactin levels and if they are normal
> then giving galactagogues is useless  ie. their reason for working, when
> they do, is by boosting a too-low level of prolactin (serum), so that milk
> prolactin may be normal and hence milk production occur.  His point being
> that to increase prolactin levels in a woman with normal levels will not
> influence her to make more milk.
> That's my understanding to date.... how does it sound?

The lactocytes transfer prolactin from blood to milk (so the prolactin milk
concentration should reflect the uptake of prolactin into the lactocyte).

 Mark Cregan in his work on prolactin talks about how
   "the continued presence of prolactin in milk throughout lactation
suggests that the mammary gland maintains an uptake of prolactin from the
blood even as the concentration of blood prolactin declines, and that this
uptake is sufficient to maintain milk production."

And because of this he says

"the emphasis on the role for prolactin in the regulation of milk synthesis
has now shifted away from the concentration of prolactin in the blood onto
the activation of the prolactin receptor located on the basement membrane,
and the subsequent internalization of blood prolactin into the lactocyte."

 He has a very nice paper researching  & discussing the effects of alveoli
distention on prolactin uptake into the lactocyte.
For the die-hard the reference is
Cregan, Mitoulas & Hartmann. 2002. Milk prolactin, feed volume & duration
between feeds in women breastfeeding their full term infants over a 24 hour
period. Experimental Physiology. 87(2):207-214

I can send you a PDF copy if you're "really really" interested

With regard to galactogogues, in more work done by Mark on intitiation of
lactation in pre term expressing women he found markers for delayed
initiation in 82% of women on Day 5. They all had normal serum prolactin
levels.

So here I have to disagree with Peter, certainly - clinically - we have all
seen that galactogogues have worked for women (whom we assume probably have
normal prolactin levels as evidenced by Mark's work) so we have to ask
ourselves how else might they be working to effect an increase in supply.
Perhaps the doses cause a sudden surge in prolactin levels that mimic what
we normally see after suckling in early lactation, and this may stimulate
increased uptake into the cell. Perhaps they in some way effect the
receptors directly, perhaps increase their number or their sensitivity. But
at this stage it does seem they must do something other than just raise
basal prolactin levels - if indeed we really are seeing an increase in
production in response to their administration. We still do need a clinical
trial to confirm this. They were doing one in Adelaide but I think it was
never finished due to funding problems.

Regards
Cathy Fetherston
Perth, Western Australia

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