Changes in cytochrome P450 isozymes (CYPs) protein levels during lactation in rat liver

Prolactin Upregulates Female-Predominant P450 Gene Expressions and Downregulates Male-Predominant Gene Expressions in Mouse Liver

Prolactin is a polypeptide hormone with over 300 separate biologic activities. Its serum level is increased during pregnancy and lactation, and it has been reported that pregnancy and lactation affect drug and steroid metabolism in mice and humans. Several studies reported that pregnancy or lactation influences liver cytochrome P450 (P450) expression and its activity, affecting the biosynthesis of steroids and xenobiotics through growth hormone or sex hormones; however, the role of prolactin as the regulator of liver P450 expression has not been elucidated so far. In the present study, we focused on prolactin as the regulator of expression of liver sex-predominant genes, including P450s. To investigate the role of prolactin in the hepatic gene expressions, pCAGGS expression vector containing mouse prolactin cDNA was transfected by hydrodynamic injection into both male and female mice. Hyperprolactinemia phosphorylated signal transducer and activator of transcription 5 in the liver and augmented female mouse liver mRNA expression of Cyp3a16, Cyp3a41, Cyp3a44, Cyp2b9, and prolactin receptor genes, whose expressions were female-predominant in hepatocytes. Moreover, liver expression of male-predominant genes such as Cyp2d9, Cyp7b1, Mup1, and Alas2 were reduced in male mice with hyperprolactinemia. The serum levels of conventional regulators of hepatic gene expressions, growth hormone, and testosterone were not affected by hyperprolactinemia. We demonstrated that prolactin upregulated female-predominant genes in female mice and downregulated male-predominant genes in male mice. We conjecture that higher concentration of prolactin would alter steroid and xenobiotic metabolisms by modulating hepatic P450 gene expressions during pregnancy and lactation.

Selective transfer of persistent organic pollutants and their metabolites in grey seals during lactation

Twenty grey seal (Halichoerus grypus) mother-pup pairs from the colony of the Isle of May (Scotland) were sampled at early and late lactation in order to study the transfer of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and their metabolites (HO-PCBs and HO-PBDEs) as well as organochlorine pesticides (OCPs), such as DDT and metabolites (DDXs) and hexachlorobenzene (HCB). The transfer of the naturally produced MeO-PBDEs was also investigated. Generally, concentrations (on a lipid weight basis) of the sum of PCBs, PBDEs and DDXs tended to be higher in all tissues at late lactation (for maternal outer blubber ΣPCBs=3860±2091 ng/g, ΣPBDEs=120±74 ng/g and ΣDDXs=559±207 ng/g; for maternal inner blubber ΣPCBs=4229±3274 ng/g, ΣPBDEs=148±118 ng/g and ΣDDXs=704±353 ng/g; for maternal serum ΣPCBs=1271±796 ng/g, ΣPBDEs=27±16 ng/g and ΣDDXs=242±125 ng/g; for milk ΣPCBs=1190±747 ng/g, ΣPBDEs=55±36 ng/g and ΣDDXs=357±160 ng/g; for pup serum ΣPCBs=1451±901 ng/g, ΣPBDEs=48±31 ng/g and ΣDDXs=395±201 ng/g). In all tissues, ΣMeO-PBDEs were found at very low levels or even undetected and their concentrations appeared to increase at late lactation only in maternal inner blubber (2.7±1.3 to 5.3±2.9 ng/g for early and late lactation, respectively) and milk (0.6±0.3 to 1.1±0.5 ng/g for early and late lactation, respectively). The transfer from inner blubber to maternal serum was selective and strongly depended on the log K(ow) value of the compounds, with less lipophilic compounds being more efficiently released. Only a limited amount of HO-PCBs was transferred during lactation as 4-HO-CB-107 was the only metabolite detected in milk (29 to 40 pg/g lw). On the contrary, most of HO-PCB metabolites found in maternal serum were also detected in pup serum. These findings suggest not only a transplacental transfer of HO-PCBs from mothers to pups but also the possibility of endogenous biotransformation in suckling pups or accumulation of undetectable low amounts from milk.

Developmental triclosan exposure decreases maternal, fetal, and early neonatal thyroxine: a dynamic and kinetic evaluation of a putative mode-of-action

This work tests the mode-of-action (MOA) hypothesis that maternal and developmental triclosan (TCS) exposure decreases circulating thyroxine (T4) concentrations via up-regulation of hepatic catabolism and elimination of T4. Time-pregnant Long-Evans rats received TCS po (0-300mg/kg/day) from gestational day (GD) 6 through postnatal day (PND) 21. Serum and liver were collected from dams (GD20, PND22) and offspring (GD20, PND4, PND14, PND21). Serum T4, triiodothyronine (T3), and thyroid-stimulating hormone (TSH) concentrations were measured by radioimmunoassay. Ethoxy-O-deethylase (EROD), pentoxyresorufin-O-depentylase (PROD) and uridine diphosphate glucuronyltransferase (UGT) enzyme activities were measured in liver microsomes. Custom Taqman(®) qPCR arrays were employed to measure hepatic mRNA expression of select cytochrome P450s, UGTs, sulfotransferases, transporters, and thyroid hormone-responsive genes. TCS was quantified by LC/MS/MS in serum and liver. Serum T4 decreased approximately 30% in GD20 dams and fetuses, PND4 pups and PND22 dams (300mg/kg/day). Hepatic PROD activity increased 2-3 fold in PND4 pups and PND22 dams, and UGT activity was 1.5 fold higher in PND22 dams only (300mg/kg/day). Minor up-regulation of Cyp2b and Cyp3a expression in dams was consistent with hypothesized activation of the constitutive androstane and/or pregnane X receptor. T4 reductions of 30% for dams and GD20 and PND4 offspring with concomitant increases in PROD (PND4 neonates and PND22 dams) and UGT activity (PND22 dams) suggest that up-regulated hepatic catabolism may contribute to TCS-induced hypothyroxinemia during development. Serum and liver TCS concentrations demonstrated greater fetal than postnatal internal exposure, consistent with the lack of T4 changes in PND14 and PND21 offspring. These data support the MOA hypothesis that TCS exposure leads to hypothyroxinemia via increased hepatic catabolism; however, the minor effects on thyroid hormone metabolism may reflect the low efficacy of TCS as thyroid hormone disruptor or highlight the possibility that other MOAs may also contribute to the observed maternal and early neonatal hypothyroxinemia.

Effects of pregnancy and lactation on warfarin-induced changes in blood coagulation-related parameters in rats

Effects of pregnancy and lactation on warfarin-induced changes in blood coagulation-related parameters were examined in rats. Warfarin (0.5 mg/kg/day) was given orally to pregnant and non-pregnant rats for 3 days from gestation day (GD) 17 to 19 or to lactating and non-pregnant rats for 3 days from post partum day (PPD) 10 to 12. Blood samples were collected from the rats on the day following the last administration (GD 20 or PPD 13) to measure prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen (FIB), thrombotest (TBT), factor VII and X activities and anti-thrombin III concentration (ATIII). Administration of warfarin to non-pregnant rats resulted in significant prolongation of APTT and TBT and significant decreases in factor VII and X activities. On the other hand, similar but not significant changes were observed in pregnant rats and similar significant but less prominent changes were observed in lactating rats. The reduction of the anticoagulant effects of warfarin may partially be related to high plasma 17beta-estradiol concentration in pregnant rats and to high plasma prolactin concentration in lactating rats, respectively.

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.

Gene expression profiles of drug-metabolizing enzymes (DMEs) in rat liver during pregnancy and lactation

A cDNA microarray analysis was conducted to examine hepatic gene expression profiles in pregnant and lactating F344 rats compared to a virgin control group using an Affymetrix GeneChip system. Of the approximately 16000 gene transcripts interrogated, more than 1000 were significantly modified in their expression when detected either in late pregnancy (19 days of gestation, GD 19, 513 genes upregulated and 579 downregulated) or on the day of delivery (postpartum 0 day, PPD 0, 497 upregulated and 733 downregulated). Particular interest was paid to the gene expression of drug-metabolizing enzymes (DMEs) and nuclear receptors (NRs). Though the expression of a few genes, those for CYP7A1, CYP51 and Sultx3, increased, the expression of a number of genes encoding DMEs (Phase I and Phase II) and NRs decreased during pregnancy and lactation. Changes in the expression of 9 genes encoding DMEs and NRs were confirmed by quantitative real-time PCR. For all 9 genes tested, overall, the results of the microarray and real-time PCR analyses were in agreement. This is the first application of a microarray analysis to the expression profiling of genes encoding DMEs and NRs in the liver of pregnant and lactating rats. When combined with other studies, the present study may provide a basis for investigating the mechanism of toxicity of environmental or other nonphysiologic chemicals to the fetus and mother and drug safety during pregnancy and lactation.