Mitogenic activity of lamb mammary fat pad in vitro is distinct
from that of mouse mammary fat pad
R.C. Hovey, T.B. McFadden, D.D.S. Mackenzie
AgResearch, Ruakura Agricultural Research Centre, Private Bag 3123,
Hamilton, New Zealand
Proceedings of the New Zealand Society of Animal Production. 1995,
55: 23-25
Our previous findings have shown that a diffusible factor(s) from
the mouse mammary fat pad (MFP) markedly enhances the growth of
COMMA-1D mouse mammary epithelial cells in response to insulin-like
growth factor-I (IGF-I) and epidermal growth factor (EGF). In these
experiments we examined whether MFP from prepubertal ewe lambs is a
source of a similar diffusible mitogenic activity. MFP tissue was from
lambs slaughtered at either 1 or 5 weeks of age. COMMA-1D cells was
plated into 24-well plates at 5x10(4) or 1x10(5) cells/well, and
quiesced in DMEM basal medium (BM). COMMA-1D cells were co-
cultured with MFP by floating an explant of MFP in the appropriate cultures
for 5 days. Conditioned medium (CM) was prepared by incubating MFP
tissue in BM for 48 hours; cells were then cultured in CM for 3 days. In all
experiments lamb MFP increased cell number by 2-3 fold relative to BM
controls (P<0.015). This mitogenic effect was additive to that of 10%
foetal calf serum. Cell number was increased by IGF-I (100NG/ML), EGF
(25ng/ml) or their combination when added to BM (P<0.03). In contrast
to the marked interactions with mouse MFP, these growth factors were
typically additive with co-cultured lamb MFP (P<0.05), although there
was a slight but significant interaction of IGF-I and MFP (P=0.048).
Cell number increased with the proportion of CM added to cultures wither
alone, or with the addition of IGF-I,EGF or IGF-I + EGF. Bovine
somatotropin (1 (ug/ml) in culture medium did not stimulate growth in
the absence or presence of lamb MFP (P>0.05). These results show that
the MFP of prepubertal lambs is the source of a diffusible mitogen(s).
This activity differs to that from mouse MFP as it does not markedly
interact with specific growth factors to stimulate the growth of COMMA-
1D cells.
Keywords: NZSAPAB;
lamb; mammary; fat pad; mouse; epithelium; growth factors
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Last Updated 25-01-1997
