Studies on the mode of oestrogenic inhibition of hepatic synthesis of alpha2u-globulin and its corresponding messenger ribonucleic acid in rat liver

Changes of serum alpha 2u-globulin in the subacute oral toxicity study of ethynyl estradiol and bisphenol A based on the draft protocol for the 'Enhanced OECD Test Guideline No. 407'

To investigate the usefulness of serum alpha 2u-globulin changes as a new parameter for detecting endocrine-mediated effects, we performed a 28-day repeated-dose toxicity study using the administration of bisphenol A (BPA) or ethynyl estradiol (EE) in male rats, based on the draft protocol of the 'Enhanced OECD Test Guideline 407 (enhanced TG 407)'. BPA at doses of 0, 40, 200 and 1000 mg/kg per day or EE at doses of 0, 15, 75 and 375 microg/kg per day were orally administered to SD rats. The highest dose of BPA was reduced to 600 mg/kg per day from the second week of the study onwards because a male rat given 1000 mg/kg per day of BPA died within the first week, showing toxic clinical signs. In the assay using BPA, a reduction in the level of alpha 2u-globulin was detected in the group receiving a dose of 600 mg/kg per day. Reductions in the absolute and relative ventral prostate weights were only observed in the 600 mg/kg per day group. In the assay using EE, the alpha 2u-globulin level decreased significantly in the 375 microg/kg per day group. A reduction in the absolute and relative dorsolateral prostate weights was also observed in the 75 and 375 microg/kg per day groups, morphologically abnormal sperm were observed in the 375 microg/kg per day group. Furthermore, atrophic changes in the prostate and seminal vesicle and degenerative changes in the testis were observed in the 375 microg/kg per day group. Although the alpha 2u-globulin level was reduced in this assay using BPA and EE, further studies are necessary before this assay becomes a useful method for detecting endocrine-mediated effects.

Cell-specific and hormonal regulation of the rat kidney androgen-regulated protein (KAP) gene

In mouse kidney, the kidney androgen-regulated protein (KAP) gene is regulated in a sex-dependent manner by a complex tissue- and cell-specific multihormonal system. KAP is also found in mouse uterus during the period surrounding birth. We describe here for the first time the existence of KAP in a species other than mouse. The rat cDNA sequence was determined and the derived peptide sequence displayed only 53% identity with murine KAP, although the genomic organization of the genes was identical. Expression of rat KAP was restricted to kidney and uterus, but was constitutive in the latter and drastically induced at parturition. The renal expression of the rat KAP gene was sexually dimorphic and regulated by physiological levels of steroid hormones. The effects of castration, hypophysectomy, thyroidectomy, and castration plus thyroidectomy on KAP mRNA levels in both kidney and uterus were determined. Constitutive expression of the protein was strictly dependent on thyroid hormone in female kidneys where it was modulated by estrogens and other ovarian factor(s). In the uterus, KAP mRNA was mainly under estrogen control. In males, expression of the KAP gene was under the dual regulation of thyroid hormone and androgens. Its complex regulation suggests a carefully delineated role for KAP in the kidney and uterus, but its physiological function remains unknown.

Changes in transcriptional activity and matrix association of alpha 2u-globulin gene family in the rat liver during maturation and aging

Hepatic synthesis of alpha 2u-globulin in the male rat begins at puberty (about 40 days), reaches a peak level at about 80 days, and ceases at about 750-800 days of age. The age-dependent changes in alpha 2u-globulin synthesis are correlated with both the steady-state level of the hepatic mRNA for this protein and the rate of transcription of the alpha 2u-globulin gene family. Transcriptional activation of the alpha 2u-globulin gene family at puberty and cessation of transcription at senescence correlate with the association and dissociation of this gene domain with the nuclear matrix. Unlike the alpha 2u-globulin gene, the albumin gene in the liver shows preferential association with the nuclear matrix throughout the life. From these results we conclude that the age-dependent changes in alpha 2u-globulin synthesis are due to the alteration in the rate of transcription of the alpha 2u-globulin gene, and that the association of this gene domain to the nuclear matrix is a prerequisite to its transcriptional activation.

Comparison of the 5' upstream putative regulatory sequences of three members of the alpha 2u-globulin gene family

We have isolated and characterized seven members of the alpha 2u-globulin gene family from a rat genomic library. The 5' upstream region (up to 1250 base pairs starting from the EcoRI site in exon 2) of three clones was sequenced. The major transcriptional start points were located 25 base pairs downstream from the 'TATA' box. A very high degree of homology was observed over the entire studied region. Two of the examined genes displayed structural features which suggest that their expression may be impeded. A high degree of homology was observed between the promotor regions of alpha 2u-globulin and those of the major urinary protein (MUP) multigene family of the mouse. A remarkable feature is the variable length of an A-rich region between the putative 'CAAT' and the 'TATA' consensus sequences. The size of this region differs markedly between MUP and alpha 2u-globulin and between different members of the alpha 2u-globulin gene family. Comparison of the alpha 2u-globulin promotor with the corresponding region of other androgen-dependent genes (the C1, C2 and C3 subunits of prostatic steroid binding protein) reveals the presence of an A-rich region of homology located approximately 378 base pairs upstream from the cap site in the alpha 2u-globulin genes. This region compares well with a sequence of putative enhancer function previously demonstrated in the alpha-fetoprotein promotor and in the immunoglobulin heavy chain promoter.

The mode of growth hormone administration is of major importance for the excretion of the major male rat urinary proteins

Male and female urinary proteins were analysed using chromatofocusing. Male rat urine had a higher protein content (measured as UV absorbance), particularly in the pI range 5.0-5.5, where female rat urine seemed to lack UV-absorbing material. The molecular weight of the major male rat urinary protein(s) is approximately 16 000 according to sodium dodecylsulphate (SDS)-polyacrylamide gel electrophoresis. The regulation of the major male rat urinary protein(s) (pI 5.3; MRUP) was studied in normal male rats and hypophysectomized rats treated for 1 week with various hormones. Urine was collected during the last day of hormone treatment and analysed by chromatofocusing and SDS-polyacrylamide gel electrophoresis. It was found that estrogen treatment of male rats suppressed the appearance of MRUP. This 'feminizing' effect was also observed following continuous infusion for 1 week of human growth hormone (hGH) or rat growth hormone (rGH) in male rats. Single injections of hGH, however, given once daily for 1 week and supplemented with glucocorticoid, thyroid hormone and androgen had an opposite effect and induced MRUP in hypophysectomized male rats. It is concluded that the mode of administration of GH is of great importance for the effects of the hormone and that continuous, as compared to intermittent, administration of GH may result in suppression or induction, respectively, of major male rat urinary protein(s).

Reversible alteration of hepatic messenger RNA species for peroxisomal and non-peroxisomal proteins induced by the hypolipidaemic drug Wy-14,643

Extensive peroxisomal proliferation in the hepatic parenchymal cells was observed when male rats were given a diet containing 0.1% Wy-14,643 [( 4-chloro-6-(2,3-xylidino)-2-pyrimidinylthio]acetic acid), a potent lipid-decreasing drug. This drug also caused a marked increase in the concentrations of the mRNA species coding for four proteins with Mr 77000, 61000, 43000 and 31000, and a similar decrease in the concentrations of three mRNA species coding for proteins of Mr 25000, 24000 and 19000. Specific immunoprecipitation studies identified the proteins of Mr 19000, 43000 and 77000 as alpha 2u-globulin, 3-ketoacyl-CoA thiolase (EC 2.3.1.16) and enoyl-CoA hydratase (EC 4.2.1.17) respectively. Comparisons of the Mr values suggest that the 61000- and 31000-Mr proteins may be equivalent to two additional peroxisomal enzymes, namely catalase (Mr 61000) and uricase (Mr 31000). The identity of the mRNA species coding for the 25000- and 24000-Mr proteins is at present unknown.

Different forms of alpha 2u-globulin in male and female rat urine

alpha 2u-Globulin is usually considered to be present only in male rat urine. This study demonstrates that a very similar protein exists in female rat urine and compares its properties with those of the male form. Isoelectric focusing followed by immunofixation reveals considerable microheterogeneity of alpha 2u-globulin in male and female rat urine. Important sex differences are noted in the banding pattern. The isoelectric point of the major male component (pI approximately equal to 5.3) is considerably higher than that of the major female components (pI approximately equal to 4.6). In addition, the female form of alpha 2u-globulin has a somewhat higher mobility on sodium dodecyl sulphate/polyacrylamide gel electrophoresis than its male counterpart. These sex differences are preserved after purification of alpha 2u-globulin from male and female rat urine by affinity chromatography and enrichment of the major male and female components by ion-exchange chromatography. Immunologically no differences are observed between these purified components and their amino acid composition reveals only minor differences. A slightly higher carbohydrate content is observed in the major female component than in the major male component. Finally evidence is presented that oestrogen treatment suppresses the male forms of alpha 2u-globulin but has no effect on the female forms. The observed differences between the male and female forms and their different hormonal control suggest that they are encoded by different genes.

Hormonal regulation of a new female-specific serum protein (FP) of the laboratory rat

This paper reports evidence for a hormonal regulation of a new rat serum protein (female specific protein, FP) which is only demonstrable in female rats. Male and female rats were treated with testosterone and estrogen. The FP was assayed with immunological methods. The following results were obtained: 1. In testosterone-treated females the serum level of FP is reduced significantly 2. In estrogenized males the FP was distinctly demonstrable but not in the control males.

Superinduction of alpha 2u globulin by actinomycin D: evidence for drug-mediated increase in alpha 2u mRNA

Actinomycin D, an inhibitor of DNA-dependent RNA synthesis, increased the hepatic concentration of alpha 2u globulin, an androgen-inducible protein in the rat. Spayed female rats with a marginally induced state of alpha 2u synthesis showed an approximately 5-fold increase in hepatic alpha 2u globulin within 3-6 hr after treatment with actinomycin D. Initial treatment of these animals with 5 alpha-dihydrotestosterone, followed by actinomycin D, resulted within 2-3 hr in a more than 2-fold increase in hepatic alpha 2u globulin compared to animals treated with the androgen alone. In spite of inhibition of hepatic synthesis of poly(A)-containing RNA to less than 25% of control, superinduction with actinomycin D resulted in a parallel increase in the translatable mRNA for alpha 2u globulin. These results showing increase in both alpha 2u globulin and its translatable mRNA after superinduction with actinomycin D support the concept of post-transcriptional repression of alpha2u synthesis.

Testosterone regulates the synthesis of major proteins in rat ventral prostate

The presence of three major proteins alpha, beta and gamma in rat ventral prostate was demonstrated by electrophoresis in polyacrylamide gels containing sodium dodecyl sulphate. Their regulation by androgens was studied by measuring the rates of synthesis of the proteins in minced prostatic tissue by using L-[35S]methionine. The three proteins account for 30-40% of the proteins synthesized in the gland. After castration, their rates of synthesis rapidly decline to about 1% that of normal animals, and this cannot be accounted for by the accompanying decrease in general protein synthesis. Testosterone reverses these changes in castrated animals, so that after 4 days normal synthesis is restored. The regulation is specific for androgens, since cyproterone acetate, an anti-androgen, is inhibitory and oestradiol-17beta and corticosterone are without effect. Preliminary characterization of the proteins indicates that protein alpha (mol.wt. 22000, pI unknown) is a glycoprotein containing glucose and/or mannose residues and occurs in both the mitochondrial and cytosol fractions. Protein beta (mol.wt. 12000, pI5.4) is also a glycoprotein, but is found exclusively in the cytosol fraction. Protein gamma (mol.wt. 8000, pI5.4) is also a glycoprotein, but is found exclusively in the cytosol fraction. Protein gamma (mol.wt. 8000, pI5.4) is also found exclusively in the cytosol fraction.