Effects of weaning and suckling on gamma-casein and prolactin receptor mRNA levels in the mouse mammary gland during lactation
1998
Kim, J.Y. (Tokyo Univ. (Japan)) | Mizoguchi, Y. | Kuraishi, T. | Yamaguchi, H. | Enami, J. | Aoki, F. | Imakawa, K. | Sakai, S.
In order to examine the ability of the mammary gland to express gamma-casein and prolactin receptor (PRL-R) genes at different stages of lactation, gamma-casein and PRL-R mRNA levels were determined on day 1, 5, 10 and 15 of lactation by the competitive RT-PCR. MIce were weaned for 24 hours and some of them were allowed to nurse foster pups for 6 h (6 h-suckling). At 0 h of weaning, gamma-casein and the long form of PRL-R (PRL-RL) mRNA levels were high on day 5 and 10, and on day 1, respectively. gamma-Casein and PRL-RL mRNAs decreased to their basal levels during the 24 h-weaning period. Except on day 16, gamma-casein and PRL-RL mRNA levels were elevated during the 6 h-suckling period as compared with their weaned controls (P0.05). The correlation (r) between the net decrease during the 24 h-weaning period and the net increase during the 6 h-suckling period was +0.86 in gamma-casein mRNA (P0.05) and +0.99 in PRL-RL mRNA (P0.01). The short form of PRL-RL mRNA level was low and remained unchanged throughout experiments. These data show that gamma-casein and PRL-RL mRNA levels change in a manner parallel to the ability of the mammary gland to increase gamma-casein and PRL-RL mRNA levels seen during the 6 h-suckling period
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