Expression of milk genes in ruminant mammary tissue, is it subject to
local controlling factors?
A.J. Molenaar, S.R. Davis, R.J. Wilkins
AgResearch, Ruakura Agriculture Centre, Private Bag 3123, Hamilton,
New Zealand
Proceedings of the New Zealand Society of Animal Production. 1993,
53: 163-166
Previous in situ hybridisation studies from our laboratory have shown
that expression of certain milk protein genes is very high in some areas of the
mammary glands of sheep and cattle, while in other areas containing an
abundance of fat globules, it is virtually zero. We wished to determine if this
heterogeneity was due to local variations in the concentrations of lactogenic
hormones and/or their receptors. Artificially increasing the local
concentration of lactogenic hormones in the sheep udder was attempted by
inserting time release capsules containing prolactin, hydrocortisone and
insulin directly into the gland up to one week before sacrifice. The local
concentration of prolactin, and the milk gene expression relative to controls,
appeared unchanged by the implants. The immunoreactivity of prolactin and
its receptor in the mammary epithelial cell cytoplasm and in particular, the
nuclei, were demonstrated and appeared to vary with the secretory activity of
the cell.
Keywords: NZSAPAB;
Prolactin; Prolactin Receptor; Milk gene; Mammary; Sheep; alpha-
Lactalbumin; Lactoferrin; in situ hybridisation; immunohistochemistry; Time
release implant.
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