Prolactin receptor expression in the epithelia and stroma of the rat mammary gland

Abstract

The importance of prolactin (PRL) in regulating growth and differentiation of the mammary gland is well known. However, it is not well established whether PRL acts solely on the mammary epithelia or if it can also directly affect the mammary stroma. To determine where PRL could exert its effects within the mammary gland, we investigated the levels of expression and the localization of the PRL receptor (PRLR) in the epithelia and stroma of the rat mammary gland at different physiological stages. For these studies, we isolated parenchymal-free 'cleared' fat pads and intact mammary glands from virgin, 18-daypregnant and 6-day-lactating rats. In addition, intact mammary tissues were enzymatically digested to obtain epithelial cells, free of stroma. The mammary tissues, intact gland, stroma and isolated epithelia, were then used for immunocytochemistry, protein extraction and isolation of total RNA. PRLR protein was detected in tissues using specific polyclonal antisera (PRLR-l) by immunocytochemistry and Western blot analysis. Messenger RNA for PRLR was measured by ribonuclease protection assay. Immunocytochemistry and Western blots with the PRLR-1 antisera detected PRLR in wild-type rat and mouse tissues, whereas the receptor protein was absent in tissues from PRLR gene-deficient mice. PRLR was found to be present both in the epithelia and stroma of mammary glands from virgin, pregnant and lactating rats, as determined by immunocytochemistry and Western blotting. Western blots revealed the predominance of three bands migrating at 88, 90 and 92 kDa in each of the rat mammary samples. These represent the long form of the PRLR. During pregnancy and lactation, PRLR protein increased in the epithelial compartment of the mammary gland but did not change within the stromal compartment at any physiological stage examined. We also found PRLR mRNA in both the epithelia and stroma of the mammary gland. Again, the stroma contained lower levels of PRLR mRNA compared with the epithelia at all physiological stages examined. Also, the PRLR mRNA levels within the stroma did not change significantly during pregnancy or lactation, whereas PRLR mRNA within the epithelia increased twofold during pregnancy and fourfold during lactation when compared with virgin rats. We conclude from this study that PRLR is expressed both in the stromal and epithelial compartment of the mammary gland. This finding suggests PRL may have a direct affect on the mammary stroma and by that route affect mammary gland development.

DietarySemen Vaccariaeenhances mammary development and lactation potential in rats

“…It is well established that many hormones, including GH, IGF-1 and PRL, are necessary for the growth and differentiation of the mammary gland (Camarillo et al 2001;Naylor et al 2003;Kleinberg and Ruan 2008). In the present study, it was found that dietary SV enhances lactation potential possibly due to improving serum GH, IGF-1 and PRL concentrations in dams (Table 3).…”

Induction of Multidrug Resistance Transporter ABCG2 by Prolactin in Human Breast Cancer Cells

“…We used T-47D cells as a PRLR-expressing model system since the PRL response monitored by known target genes was not observed in other mammary cell lines, such as MCF-7, MCF-10A, and primary HMEC, probably due to low PRLR expression. The expression of the functional long form of the PRLR in the mammary gland of rat and mouse is temporally regulated, showing lactationassociated up-regulation (Camarillo et al, 2001;Mizoguchi et al, 1996). Although experimental data to confirm this in humans is lacking, T-47D cells serve as a model system to study PRL signaling in the human mammary gland.…”

White Matter Plasticity and Enhanced Remyelination in the Maternal CNS

“…MBP protein levels were normalized to actin to control for differences in protein loading. The murine PRLR long form (PRLR-L) protein bands were recognized in the molecular weight range previously described by others (Ling et al, 2000;Camarillo et al, 2001).…”