Weaning induces NOS-2 expression through NF-kappaB modulation in the lactating mammary gland: importance of GSH

Calpains, the proteases of two faces controlling the epithelial homeostasis in mammary gland

Calpain-1 and calpain-2 are calcium-dependent Cys-proteases ubiquitously expressed in mammalian tissues with a processive, rather than degradative activity. They are crucial for physiological mammary gland homeostasis as well as for breast cancer progression. A growing number of evidences indicate that their pleiotropic functions depend on the cell type, tissue and biological context where they are expressed or dysregulated. This review considers these standpoints to cover the paradoxical role of calpain-1 and -2 in the mammary tissue either, under the physiological conditions of the postlactational mammary gland regression or the pathological context of breast cancer. The role of both calpains will be examined and discussed in both conditions, followed by a brief snapshot on the present and future challenges for calpains, the two-gateway proteases towards tissue homeostasis or tumor development.

The crossroads of breast cancer progression: insights into the modulation of major signaling pathways

Cancer is the disease with highest public health impact in developed countries. Particularly, breast cancer has the highest incidence in women worldwide and the fifth highest mortality in the globe, imposing a significant social and economic burden to society. The disease has a complex heterogeneous etiology, being associated with several risk factors that range from lifestyle to age and family history. Breast cancer is usually classified according to the site of tumor occurrence and gene expression profiling. Although mutations in a few key genes, such as BRCA1 and BRCA2, are associated with high breast cancer risk, the large majority of breast cancer cases are related to mutated genes of low penetrance, which are frequently altered in the whole population. Therefore, understanding the molecular basis of breast cancer, including the several deregulated genes and related pathways linked to this pathology, is essential to ensure advances in early tumor detection and prevention. In this review, we outline key cellular pathways whose deregulation has been associated with breast cancer, leading to alterations in cell proliferation, apoptosis, and the delicate hormonal balance of breast tissue cells. Therefore, here we describe some potential breast cancer-related nodes and signaling concepts linked to the disease, which can be positively translated into novel therapeutic approaches and predictive biomarkers.

EGF-Induced Acetylation of Heterogeneous Nuclear Ribonucleoproteins Is Dependent on KRAS Mutational Status in Colorectal Cancer Cells

KRAS mutational status is considered a negative predictive marker of the response to anti-EGFR therapies in colorectal cancer (CRC) patients. However, conflicting data exist regarding the variable response to EGFR-targeted therapy. The effects of oncogenic KRAS on downstream targets were studied in cell lines with different KRAS mutations. Cells harboring a single KRASG13D allele showed the most tumorigenic profile, with constitutive activation of the downstream pathway, rendering them EGF-unresponsive. Conversely, KRASA146T cells showed a full EGF-response in terms of signal transduction pathways, cell proliferation, migration or adhesion. Moreover, the global acetylome of CRC cells was also dependent on KRAS mutational status. Several hnRNP family members were identified within the 36 acetylated-proteins. Acetylation status is known to be involved in the modulation of EGF-response. In agreement with results presented herein, hnRNPA1 and L acetylation was induced in response to EGF in KRASA146T cells, whereas acetyl-hnRNPA1 and L levels remained unchanged after growth factor treatment in KRASG13D unresponsive cells. Our results showed that hnRNPs induced-acetylation is dependent on KRAS mutational status. Nevertheless hnRNPs acetylation might also be the point where different oncogenic pathways converge.

Involvement of Different networks in mammary gland involution after the pregnancy/lactation cycle: Implications in breast cancer

Early pregnancy is associated with a reduction in a woman's lifetime risk for breast cancer. However, different studies have demonstrated an increase in breast cancer risk in the years immediately following pregnancy. Early and long-term risk is even higher if the mother age is above 35 years at the time of first parity. The proinflammatory microenvironment within the mammary gland after pregnancy renders an "ideal niche" for oncogenic events. Signaling pathways involved in programmed cell death and tissue remodeling during involution are also activated in breast cancer. Herein, the major signaling pathways involved in mammary gland involution, signal transducer and activator of transcription (STAT3), nuclear factor-kappa B (NF-κB), transforming growth factor beta (TGFβ), and retinoid acid receptors (RARs)/retinoid X receptors (RXRs), are reviewed as part of the complex network of signaling pathways that crosstalk in a contextual-dependent manner. These factors, also involved in breast cancer development, are important regulatory nodes for signaling amplification after weaning. Indeed, during involution, p65/p300 target genes such as MMP9, Capn1, and Capn2 are upregulated. Elevated expression and activities of these proteases in breast cancer have been extensively documented. The role of these proteases during mammary gland involution is further discussed. MMPs, calpains, and cathepsins exert their effect by modification of the extracellular matrix and intracellular proteins. Calpains, activated in the mammary gland during involution, cleave several proteins located in cell membrane, lysosomes, mitochondria, and nuclei favoring cell death. Besides, during this period, Capn1 is most probably involved in the modulation of preadipocyte differentiation through chromatin remodeling. Calpains can be implicated in cell anchoring loss, providing a proper microenvironment for tumor growth. A better understanding of the role of any of these proteases in tumorigenesis may yield novel therapeutic targets or prognostic markers for breast cancer.

Whole-genome analyses of Korean native and Holstein cattle breeds by massively parallel sequencing

A main goal of cattle genomics is to identify DNA differences that account for variations in economically important traits. In this study, we performed whole-genome analyses of three important cattle breeds in Korea—Hanwoo, Jeju Heugu, and Korean Holstein—using the Illumina HiSeq 2000 sequencing platform. We achieved 25.5-, 29.6-, and 29.5-fold coverage of the Hanwoo, Jeju Heugu, and Korean Holstein genomes, respectively, and identified a total of 10.4 million single nucleotide polymorphisms (SNPs), of which 54.12% were found to be novel. We also detected 1,063,267 insertions–deletions (InDels) across the genomes (78.92% novel). Annotations of the datasets identified a total of 31,503 nonsynonymous SNPs and 859 frameshift InDels that could affect phenotypic variations in traits of interest. Furthermore, genome-wide copy number variation regions (CNVRs) were detected by comparing the Hanwoo, Jeju Heugu, and previously published Chikso genomes against that of Korean Holstein. A total of 992, 284, and 1881 CNVRs, respectively, were detected throughout the genome. Moreover, 53, 65, 45, and 82 putative regions of homozygosity (ROH) were identified in Hanwoo, Jeju Heugu, Chikso, and Korean Holstein respectively. The results of this study provide a valuable foundation for further investigations to dissect the molecular mechanisms underlying variation in economically important traits in cattle and to develop genetic markers for use in cattle breeding.

Differential functions of calpain 1 during epithelial cell death and adipocyte differentiation in mammary gland involution

Calpains become activated in the mammary gland early during weaning, cleaving several proteins located mainly in the cell membrane, but also in other organelles such as lysosomes, mitochondria and nuclei. By immunofluorescence and Western blot analysis, we have demonstrated the nuclear translocation of calpain-1 and calpain-2, together with the cleavage of several cytoplasmic nucleoporins in epithelial cells of the lobulo-alveolar compartment. In vivo and in vitro calpain inhibition prevented this nucleoporin degradation. In addition, calpain-1 was also present in the nucleus of non-epithelial mammary tissue cells, concomitant with adipocyte re-differentiation. Calpain-1 was internalized within nuclei and found to be present in the nuclear chromatin-enriched fraction, associated with histone H3. Furthermore, we have demonstrated, both in vivo and in vitro, the cleavage of the N-terminal residue of histone H3 by calpain-1. Calpain-1 co-localized with both H3K4me3 (histone H3 trimethylated at Lys4) and H3K27me3 (histone H3 trimethylated at Lys27) at the nuclear periphery, a bivalent epigenetic signal essential for cell differentiation. Using ChIP assays we could confirm the presence of calpain-1 in the promoters of key genes expressed in adipose tissue, such as Cebpa (CCAAT/enhancer-binding protein α) and Lep (leptin). The results of the present study highlight a dual role for calpain-1 in the weaned gland after the pregnancy/lactation cycle, controlling programmed cell death and participating in the epigenetic programme during adipocyte differentiation.

Effects of glutamine supplementation on the immune status in weaning piglets with intrauterine growth retardation

Neonates with intrauterine growth retardation (IUGR) often suffer from impaired cellular immunity, and weaning may further aggravate adverse effects of IUGR on development and function of the immune system. In this study, we investigated effects of glutamine supplementation on immune status in the intestines of weaning pigs with IUGR, focusing on molecular mechanisms underlying altered immune response. Piglets with IUGR were weaned at 21 days of age and received orally 1.22 g alanine or 1 g glutamine per kg body weight every 12 h. Weight gain and intestinal weight of weaning piglets were increased by glutamine supplementation. Levels of serum IgG in piglets supplemented with glutamine were increased compared with Control piglets. The production of IL-1 and IL-8 in the serum and jejunum was decreased by glutamine supplementation, whereas the levels of IL-4 in the serum and the concentrations of IL-4 and IL-10 in the jejunum were increased. The expression of heat shock protein 70 (Hsp70) in the jejunum was increased by glutamine supplementation, but the degradation of inhibitor κB and the activity of nuclear factor-κB (NF-κB) were decreased. In conclusion, glutamine supplementation enhanced immune response in weaning piglets with IUGR. The effects of glutamine in IUGR are associated with increased Hsp70 expression and suppression of NF-κB activation.

Calpains mediate epithelial-cell death during mammary gland involution: mitochondria and lysosomal destabilization

Our aim was to elucidate the physiological role of calpains (CAPN) in mammary gland involution. Both CAPN-1 and -2 were induced after weaning and its activity increased in isolated mitochondria and lysosomes. CAPN activation within the mitochondria could trigger the release of cytochrome c and other pro-apoptotic factors, whereas in lysosomes it might be essential for tissue remodeling by releasing cathepsins into the cytosol. Immunohistochemical analysis localized CAPNs mainly at the luminal side of alveoli. During weaning, CAPNs translocate to the lysosomes processing membrane proteins. To identify these substrates, lysosomal fractions were treated with recombinant CAPN and cleaved products were identified by 2D-DIGE. The subunit b(2) of the v-type H(+) ATPase is proteolyzed and so is the lysosomal-associated membrane protein 2a (LAMP2a). Both proteins are also cleaved in vivo. Furthermore, LAMP2a cleavage was confirmed in vitro by addition of CAPNs to isolated lysosomes and several CAPN inhibitors prevented it. Finally, in vivo inhibition of CAPN1 in 72-h-weaned mice decreased LAMP2a cleavage. Indeed, calpeptin-treated mice showed a substantial delay in tissue remodeling and involution of the mammary gland. These results suggest that CAPNs are responsible for mitochondrial and lysosomal membrane permeabilization, supporting the idea that lysosomal-mediated cell death is a new hallmark of mammary gland involution.

Changes in blood parameters and the expression of coagulation-related genes in lactating Sprague-Dawley rats

This study measured blood parameters, particularly those related to coagulation, and alterations in the expression levels of blood-coagulation-related genes in lactating Sprague-Dawley rats. The day of delivery was designated as lactation day 0 (LD 0). On the day after delivery (LD 1), prothrombin time and overall activity of vitamin-K-dependent coagulation factors were decreased, whereas fibrinogen contents, platelet counts and antithrombin III concentrations were increased as compared with those in nonpregnant rats. In addition, hepatic expression of blood-coagulation-related genes in the liver was increased at LD 0 as compared with that in nonpregnant rats. These changes may be physiologic responses to prevent prolonged bleeding at delivery. Except for fibrinogen content, which remained elevated, the described changes returned to baseline on and after LD 7. Activities of AST, ALT, and ALP were increased on LD 7, 14, and 21 as compared with nonpregnant rats. In contrast, total protein, albumin, Cl, and Ca were consistently lower on LD 7, 14, or 21 as compared with levels in nonpregnant rats. These results provide background data for evaluation of nursing rats.

Candidate pathways linking inducible nitric oxide synthase to a basal-like transcription pattern and tumor progression in human breast cancer

Inducible nitric oxide synthase (NOS2) is an inflammation responsive enzyme (EC 1.14.13.39) that is induced during acute and chronic inflammation and tissue injury as part of the host defense and wound healing process. NOS2 up-regulation leads to increased nitric oxide (NO) production, the means by which this enzyme can initiate NO-dependent signal transduction, influence the redox state of cells and induce modifications of proteins, lipids, and DNA. Aberrant expression of NOS2 has been observed in many types of human tumors. In breast cancer, increased NOS2 is associated with markers of poor outcome and decreased survival. Growth factor and cytokine signaling, tissue remodeling, NF-kB activation, and hypoxia are candidate mechanisms that induce NOS2 in tumor epithelial and tumor-infiltrating cells. NOS2 induction will trigger the release of variable amounts of NO into the tumor microenvironment and can activate oncogenic pathways, including the Akt, epidermal growth factor receptor and c-Myc signaling pathways, and stimulate tumor microvascularization. Constitutively increased NO levels may also select for mutant p53 cells to overcome the tumor suppressor function of NO-activated wild-type p53. More recent findings suggest that NO induces stem cell-like tumor characteristics in breast cancer. In this review, we will discuss the effects of NO in tumor biology and disease progression with an emphasis on breast cancer, and will examine the mechanisms that link increased NO to a basal-like transcription pattern in human breast tumors and poor disease outcome.

Inflammatory responses in epithelia: endotoxin-induced IL-6 secretion and iNOS/NO production are differentially regulated in mouse mammary epithelial cells

Background

IL-6 is a pro-inflammatory cytokine that signals via binding to a soluble or membrane bound receptor, while nitric oxide (NO), an oxidative stress molecule, diffuses through the cell membrane without a receptor. Both mediators signal through different mechanisms, yet they are dependent on NFκB. We proposed that both mediators are co-induced and co-regulated in inflamed mammary epithelial cells.

Methods

SCp2 mammary epithelial cells were treated with bacterial endotoxin (ET) for different time periods and analyzed for induction of IL-6 secretion and NO production by ELISA and Griess reaction, respectively. The expression of IL-6 and induced NO synthase (iNOS) was assayed by real time PCR and/or western immunoblots, and the activation of NFκB was assayed by immunobinding assay. To investigate the role of mammary cell microenvironment (cell-substratum or interaction of mammary epithelial cell types; critical to mammary development, function, and disease) in modulation of the inflammatory response, SCp2 cells were cultured with or without extracellular matrix (EHS) or in coculture with their myoepithelial counterpart (SCg6), and assayed for ET-induced IL-6 and NO.

Results

Endotoxin induced NFκB activation at 1 h after ET application. IL-6 secretion and NO production were induced, but with unexpected delay in expression of mRNA for iNOS compared to IL-6. NFκB/p65 activation was transient but NFκB/p50 activation persisted longer. Selective inhibition of NFκB activation by Wedelolactone reduced ET-induced expression of IL-6 mRNA and protein but not iNOS mRNA or NO production, suggesting differences in IL-6 and iNOS regulation via NFκB. SCp2 cells in coculture with SCg6 but not in presence of EHS dramatically induced IL-6 secretion even in the absence of ET. ET-induced NO production was blunted in SCp2/SCg6 cocultures compared to that in SCp2 alone.

Conclusions

The differential regulation of IL-6 and iNOS together with the differential activation of different NFκB dimers suggest that IL-6 and iNOS are regulated by different NFκB dimers, and differentially regulated by the microenvironment of epithelial cells. The understanding of innate immune responses and inflammation in epithelia and linkage thereof is crucial for understanding the link between chronic inflammation and cancer in epithelial tissues such as the mammary gland.

Nitric oxide triggers mammary gland involution after weaning: remodelling is delayed but not impaired in mice lacking inducible nitric oxide synthase

During mammary gland involution, different signals are required for apoptosis and tissue remodelling. To explore the role of NO in the involution of mammary tissue after lactation, NOS2 (inducible nitric oxide synthase)-KO (knockout) mice were used. No apparent differences were observed between NOS2-KO and WT (wild-type) animals during pregnancy and lactation. However, upon cessation of lactation, a notable delay in involution was observed, compared with WT mice. NOS2-KO mice showed increased phosphorylation of STAT (signal transducer and activator of transcription) 5 during weaning, concomitant with increased β-casein mRNA levels when compared with weaned WT glands, both hallmarks of the lactating period. In contrast, activation of STAT3, although maximal at 24 h after weaning, was significantly reduced in NOS2-KO mice. STAT3 and NF-κB (nuclear factor κB) signalling pathways are known to be crucial in the regulation of cell death and tissue remodelling during involution. Indeed, activation of both STAT3 and NF-κB was observed in WT mice during weaning, concomitant with an increased apoptotic rate. During the same period, less apoptosis, in terms of caspase 3 activity, was found in NOS2-KO mice and NF-κB activity was significantly reduced when compared with WT mice. Furthermore, the activation of the NF-κB signalling pathway is delayed in NOS2-KO mice when compared with WT mice. These results emphasize the role of NO in the fine regulation of the weaning process, since, in the absence of NOS2, the switching on of the cascades that trigger involution is hindered for a time, retarding apoptosis of the epithelial cells and extracellular matrix remodelling.

Eccentric exercise induces nitric oxide synthase expression through nuclear factor-κB modulation in rat skeletal muscle

This study aimed to investigate the effect of eccentric exercise on the expression of the different nitric oxide synthase (NOS) isoforms in rat deep vastus lateralis muscle. Twenty-four rats were allocated to four experimental groups: rested control group, acutely exercised group after an intermittent downhill protocol for 90 min, acutely exercised group treated with pyrrolidine dithiocarbamate (100 mg/kg ip) for 24 and 1 h before the acute exercise bout, and acutely exercised group with a previous submaximal eccentric training of 8 wk. Acutely exercised rats showed increased levels of protein tyrosine nitration, NF-κB binding, and phospho-IκBα content. A significant increase was observed in mRNA level and protein content of neuronal NOS, inducible NOS, and endothelial NOS. The binding of NF-κB to the NOS isoform promoters, measured by a chromatin immunoprecipitation assay, was undetectable in rested rats, whereas it was evident in acutely exercised animals. All of these effects were partially abolished by pyrrolidine dithiocarbamate treatment and by training. In summary, our findings provide a direct link between the NF-κB signaling cascade and NOS expression in skeletal muscle following eccentric exercise and suggest a modulation of the expression of the three NOS isoforms by this transcription factor.

Carbon tetrachloride-induced hepatotoxicity in pregnant and lactating rats

Carbon tetrachloride (CCl4) is well known to induce hepatotoxicity after being metabolized to trichloromethyl free radical ((.)CCl3) by CYP2E1. In the present study, the hepatotoxicity induced by a single oral dose (2,000 mg/kg) of CCl4 was compared between pregnant (gestation days (GD) 13 and 19) or postpartum (postpartum days (PPD) 1, 13 and 27) and non-pregnant rats. Hepatotoxicity in CCl4-treated pregnant rats evaluated by blood chemistry (alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) activities) and histopathological finding (area of damaged hepatocytes) was minimal on GD19, being weaker than that in non-pregnant rats. CYP2E1 expression in non-treated pregnant rats decreased as pregnancy progressed and reached minimum level on GD19. Thus, the degree of CCl4-induced hepatotoxicity roughly corresponded to CYP2E1 levels during pregnancy. After delivery, hepatotoxicity in CCl4-treated lactating rats was maximal on PPD13, being stronger than that in non-pregnant rats, and then it decreased slightly on PPD27. The CYP2E1 level in the non-treated lactating rats tended to increase but remained at lower levels until PPD13 compared with that in non-pregnant rats. Thus, the degree of CCl4-induced hepatotoxicity did not correspond to CYP2E1 levels during lactation. This suggests that during lactation, there may be certain factors other than CYP2E1 expression responsible for the degree of CCl4-induced hepatotoxicity.

Differentiation of the mammary epithelial cell during involution: implications for breast cancer

That milk secretion is not the final differentiated state of the mammary alveolar cells is a relatively new concept. Recent work has suggested that secreting, mammary epithelial cells (MECs) have another function to perform before they undergo cell death in the involuting mammary gland. That is, they help in the final clearance and breakdown of their neighboring cells (and likely residual milk as well.) They become, for a short time, amateur phagocytes, or efferocytes, and then are believed to die and be cleared themselves. Although relatively little study has been made of this change in the functional state of the MEC, nevertheless we may speculate from the involution literature, and extend findings from other systems of apoptotic cell clearance, on some of the mechanisms involved. And with the finding that involution may represent a unique susceptibility window for the progression of metastatic breast cancer, we may suggest areas for future research along these lines as well.

The role of cathepsins in involution and breast cancer

Cysteine cathepsins are proteolytic enzymes that reside in endolysosomal vesicles. Some are expressed constitutively while others are transcriptionally regulated. However, the expression and subcellular localization of cathepsins changes during cancer progression and cathepsins have been shown to be causally involved in various aspects of tumorigenesis including metastasis. The use of mouse models of breast cancer genetically ablated for cathepsin B has shown that both the growth of the primary tumor and the extend of lung metastasis is reduced by the loss of cathepsin B. The role of cathepsins in involution of the mammary gland has received little attention although it is clear that cathepsins are involved in tissue remodeling in the second phase of involution. We discuss here the roles of cathepsins and their endogenous inhibitors in breast tumorigenesis and post-lactational involution.

Nitration of cathepsin D enhances its proteolytic activity during mammary gland remodelling after lactation

Proteomic studies in the mammary gland of control lactating and weaned rats have shown that there is an increased pattern of nitrated proteins during weaning when compared with controls. Here we report the novel finding that cathepsin D is nitrated during weaning. The expression and protein levels of this enzyme are increased after 8 h of litter removal and this up-regulation declines 5 days after weaning. However, there is a marked delay in cathepsin D activity since it does not increase until 2 days post-weaning and remains high thereafter. In order to find out whether nitration of cathepsin D regulates its activity, iNOS (inducible nitric oxide synthase)−/− mice were used. The expression and protein levels of this enzyme were similar to WT (wild-type) animals, but the proteolytic activity was significantly reduced during weaning in knockout compared to WT mice. in vitro treatment of recombinant human cathepsin D or lactating mammary gland homogenates with relatively low concentrations of peroxynitrite enhances the nitration as well as specific activity of this enzyme. Using MS, it has been shown that the residue Tyr168 was nitrated. All of these results show that protein nitration during weaning might be a signalling pathway involved in mammary gland remodelling.

Retinoids induce MMP-9 expression through RARalpha during mammary gland remodeling

Retinoic acid (RA) is a signaling molecule in the morphogenesis of the mammary gland, modulating the expression of matrix metalloproteinases (MMPs). The aim of this paper was to study the role of RA during weaning, which consists of three events: apoptosis of the secretory cells, degradation of the extracellular matrix, and adipogenesis. CRABP II and CRBP-1 carrier proteins increased significantly during weaning compared with lactating glands but reverted to control values after the litter resuckled. The effects of RA are mediated by the nuclear receptors RARalpha, RARbeta, RARgamma, and RXRalpha, which underwent an increase in protein levels during weaning. In an attempt to elucidate the RARalpha-dependent signaling pathway, ChIP assays were performed. The results showed the binding of RARalpha to the MMP-9 promoter after 24- and 72-h weaning together with its coactivator p300; this fact could be responsible for the increase found in MMP-9 mRNA and protein levels in these conditions. Expression of related MMPs (MMP-2 and MMP-3) was also increased during weaning. Using gelatine zymography, we observed a time-dependent increase in active forms of MMP-9 and MMP-2. On the other hand, the inhibitor of MMPs, TIMP-1, was almost undetectable at 24- and 72-h weaning by Western blot. The role of retinoids in matrix remodeling is reinforced by the fact that administration of an acute dose of retinol palmitate to control lactating rats also induces MMP-9 expression. This emphasizes the importance of retinoids in vivo to regulate mammary gland involution.

The declining phase of lactation: peripheral or central, programmed or pathological?

In most species the functional activity of the mammary gland during lactation follows a biphasic developmental pattern. This pattern starts with a rapid increase in milk output that occurs with secretory activation and continues with a more gradual increase until the point of peak lactation is reached. Following this gain-of-function phase, the ability of the gland to produce milk decreases. This decrease occurs even if the lactation is prolonged by the presence of continued suckling stimulus and complete milk removal. This review describes the current state of our knowledge concerning the factors that regulate milk synthesis capacity by the mammary gland during the lactation cycle. The review describes four potential alternatives as mechanisms governing the process, which we refer to as secretory diminution. These alternatives are not presented as mutually exclusive of each other or other possible mechanisms, but are proposed as potential contributing mechanisms.

Role of GSH in the modulation of NOS-2 expression in the weaned mammary gland

GSH delivery to the lactating mammary gland is essential for the maintenance of lactation as its decrease leads to apoptosis and involution of the mammary gland. In fact, it has already been demonstrated that some of the changes in gene expression found in the lactating mammary gland after forced weaning are reproduced in rats treated with buthionine sulphoximine to deplete GSH levels. An oligonucleotide microarray experiment would give us a better knowledge of the mRNA expression patterns during lactation and after weaning and the possible functions of GSH in the modulation of these events.