Jy. Mccracken et al., SPATIAL AND TEMPORAL EXPRESSION OF TRANSFERRIN GENE IN THE RAT MAMMARY-GLAND, Journal of dairy science, 77(7), 1994, pp. 1828-1834
The distribution and concentration of transferrin mRNA in the rat mamm
ary gland was analyzed using in situ hybridization, and the results we
re compared with those obtained for other milk protein mRNA. The [S-35
]RNA probes prepared from rat cDNA for transferrin and for alpha-, bet
a-, and gamma-caseins, alpha-lactalbumin, and whey acidic protein were
used to probe mammary tissue from rats in late pregnancy and at diffe
rent stages of lactation. The overall level of transferrin gene expres
sion varied in a biphasic manner, decreasing after parturition to bare
ly detectable levels at d 2 to 10 of lactation before increasing again
markedly in late lactation. This temporal pattern contrasts sharply w
ith that observed for the other genes, for which levels tended to rise
or to remain relatively stable until late lactation. The spatial patt
erns of transferrin expression were also quite distinct, and, even dur
ing the period of low expression, some alveoli showed high concentrati
ons of transferrin mRNA. In contrast, intramammary distribution of mRN
A for the other genes was relatively uniform. Our results show that th
e patterns of transferrin gene expression differ both spatially and te
mporally from those of five other milk protein genes and suggest that
transferrin gene expression is controlled by a regulatory system that
turns individual alveoli either fully on or fully off.