Adult Female Rat Liver Research Articles

Neonatal phenobarbital administration results in increased cytochrome P 450-dependent monooxygenase activity in adult male and female rats

The effects of neonatal exposure to phenobarbital during the first five days after birth on the enzymatic activity of the adult male and female rat liver P 450-dependent monooxygenase system were investigated. Although liver weight per 100 grams of body weight and total hepatic microsomal protein content were not altered in adult rats treated neonatally with phenobarbital, both sexes did show significant increases in cytochrome P 450 content, cytochrome P 450 reductase activity, cytochrome c reductase activity, ethoxycoumarin-O-deethylase activity and in the activity of a specific glucuronyl-transferase. Several of these activities were increased to a larger extent in the females, suggesting that females may be more sensitive to this phenomenon.

Age-related changes in mutagen activation by rat tissues

Age-related changes in drug metabolism of the liver, lung and kidney of adult female Long-Evans rats were determined by measuring changes in mutagen formation. Activation of aflatoxin B 1 (AFB 1), 2-aminofluorene (AF) and 2-acetylaminofluorene (AAF) to mutagenic derivatives was assayed using the Ames Salmonella test system. The promutagens were incubated with tissue fractions from rats ranging in age from 2.5 to 25 months. With all three compounds, hepatic, renal and pulmonary activation was lower in the senescent than in the young adult animals. The largest decrease, however, occurred prior to middle-age, i.e. before 9–13 months. In liver and kidney, little change was detectable between the middle-aged and the old (20–25 months) animals. However, pulmonary metabolism in the oldest animals was slightly higher than in the extracts from the middle-aged rats. The observed decline in mutagen activation may thus be a function of maturation rather than senescence.

Decreased protein synthesis by polysomes, tRNA and aminoacyl-tRNA synthetases isolated from senescent rat liver

A cell-free in vitro protein-synthesizing system isolated from adult (10–13 month) and senescent (24–30 month) female Wistar rat liver is described. Optimal concentrations of polysomes, aminoacyl-tRNA synthetases, tRNA, Mg 2+, K +, and labeled amino acids are reported for this in vitro system. Both the rate and extent of protein synthesis are lower with the system from senescent liver compared to that from adult liver. Senescent polysomes, tRNA synthetases, and tRNA all contribute to this decrease. Free adult or senescent polysomes support protein synthesis to the same extent. However, compared to adult polysomes, senescent membrane-bound polysomes support less protein synthesis and account for an increased proportion of the total polysome fraction. Ribonuclease and protease activities are low in the adult and the senescent in vitro systems and do not account for the decreased protein synthesis with the latter.

A possible physiological role of taurine in the adult female rat liver.

In agreement with previous results (Awapara, 1956), we noted that the taurine level in the liver of the adult female rat is higher than in the adult male rat: 9.44 and 2.08, respectively, expressed as a concentration (mumoles/g of liver). Furthermore, we observed a significant decrease of the taurine level (expressed similarly) in the liver of the lactating rat: 1.84 twenty-one days after the birth of pups. These observations suggest a physiological role for the higher concentration of taurine in the liver of the adult female rat: in other words, a reserve of taurine, whatever its origin in the adult female rat, may be needed for pup development.

Regulation of rat liver NADP+-isocitrate dehydrogenase during aging

In an attempt to understand the mechanism of aging in relation to the differences in enzyme regulation, the induction and kinetic properties of NADP+ -isocitrate dehydrogenase of the liver of immature (6 weeks), mature (13 weeks), adult (33 weeks) and old (85 weeks) female rats were studied. The specific activity of the cytoplasmic and mitochondrial NADP+ -isocitrate dehydrogenase increased up to the adult age (33 weeks) and decreased in the old rats (85 weeks). Overiectomy decreased and estradiol administration induced activity of both the mitochondrial and eytoplasmic enzyme in the liver ol immature, mature and adult rats but had no significant effect in old rats. However, the activity of mitochondrial NADP+ -isocitrate dehydrogenase decreased and eytoplasmic NADP+ -isocitrate dehydrogenase increased following ovariectomy in old rats (85 weeks). Hormone-mediated induction of enzyme activity was actinomycin D sensitive. The Km for isocitrate and NADP, Ki value for oxalomalate, heat stability and electrophoretic mobility of the purified enzyme from the cytosol fraction of the liver of immature and old rats were similar. It can he concluded that the enzyme does not change structurally with age.

Estrogen receptor in liver of male and female rats: endocrine regulation and molecular properties.

Estrogen receptors from livers of adult male and female rats were compared. Hepatic cytosol estrogen receptors from both sexes were similar using the criteria of percent of saturation with ammonium sulfate required for precipitation, and isoelectric point (p1) of the receptor. The estrogen receptor from male or female rat liver cytosol was maximally precipitated with ammonium sulfate at 30% of saturation (30% AS ppt). As previously described, demonstration of the estrogen receptor in liver cytosol of male rats required this partial purification step because of the presence of an additional sex hormone binder with unusual properties. The p1 of the liver cytosol receptor from females was 6.9. After 30% AS ppt, the p1 of the cytosol receptor from male or female rat livers was 4.7. Liver estrogen receptors from male or female rats had similar affinity

Use of a dimethylated oxirane to characterise microsomal mono-oxygenases in rat liver

A newly-synthesised dimethylated chlorocyclodiene epoxide is metabolised by NADPH-supplemented rat liver microsomes to produee either one or both of two major metabolites. M1 and M2. Microsomes from adult male rat liver produce both metabolites. By contrast, microsomes made from the livers of mature or immature female rats make only metabolite M1, as do hepatic microsomes from pre-pubertal male rats. Male rats castrated when 7 days old provide liver microsomes that make little of metabolite M2 upon killing at 3–5 months post partum. After induction with phenobarbital, microsomes from adult male and female rat liver make metabolites M1 and M2. together with a further unidentified metabolite. After induction with 3-methylcholanthrene, hepatic microsomes from mature female rats continue to make only metabolite M1 but to make it in larger quantities. These differences, which appear to result from the activity of three or more mono-oxygcnases. could possibly he exploited to monitor the mono-oxygenase status of rat liver microsomes.

Estrogen receptor in rat liver: translocation to the nucleus in isolated parenchymal cells.

Isolated, purified, viable parenchymal cells from adult female rat liver were characterized for their estrogen receptor distribution. The isolated cells contained cytosol-binding sites specific for [3H]estradiol ([3H]E2; determined after partial purification) at a level near that found in cytosol prepared from whole liver. The properties of these binding sites closely resembled those of putative estrogen receptors found in cytosol prepared from liver or uterus in adult female rats. The estrogen receptor distribution was then studied after exposure of the cells to ethinyl estradiol (EE2; the commonly used estrogen in oral contraceptives). After in vitro incubation with EE2, cytosol and nuclear estrogen receptors were determined by exchange assay with [([3H]E2. Cytosol receptor levels were rapidly depleted, while receptor levels in highly purified nuclei were rapidly increased. The cytosol. of cells not exposed to EE2 and nuclei of cells exposed to EE2 for 15 min contained binding sites for [([3H]E2 with si...

Solubilization of the lactogenic receptors from rat liver microsomes

Summary The receptors that bind lactogenic hormones have been solubilized from adult female rat liver microsomes with 1% (wt/v) Triton X-100. The receptors remained in the supernatant after a centrifugation at 190,000 x gav for 8 h. They could be detected by gel filtration on Sephadex G-100 and by precipition with 12% (wt/v) Polyethylene Glycol. The specific binding of [125I]hGH to the solubilized receptors reached the equilibrium within 8 h at 25°C. The solubilized binding sites retained their specificity for lactogenic hormones. The equilibrium constant for the dissociation of the complex was 8 × 10−10 M. These properties are not significantly different from those reported for the particulate preparation.

Quantitative untersuchungen zur zonalen verteilung der SDH-, G6Pase- und malatenzym-aktivitäten im leberparenchym

In native cryostat tissue sections of adult female albino rat liver the activities of succinate dehydrogenase (E. C. 1.3.99.1), glucose-6-phosphatase (E. C. 3.1.3.9) and malic enzyme (E. C. 1.1.1.40) were histochemically demonstrated and planimetrically determined. The areas of the enzymes with a maximum activity in the periportal regions, namely SDH and G-6-Pase, were respectively 34% and 41% of the whole parenchyma. Malic enzyme showed a maximum activity in the perivenous region, which consisted of about 53% of the total parenchyma. The zonal distribution of enzyme activities is related only to the terminal vessels; in the vicinity of the preterminal vessels an irregular distribution pattern was found. The results further support the assumption of the bifunctionality of liver parenchyma.

Progesterone-binding properties of microsomes from rat liver

The progesterone binding properties of microsomal suspensions from rat liver have been studied using a Dextran-coated charcoal method for the determination of the progesterone binding capacity. Microsomes isolated from the livers of adult female, male and pregnant female rats all exhibited progesterone binding of high affinity and limited capacity ( K a ∼ 2 × 10 7M −1), in addition to non-specific binding of progesterone. The high affinity progesterone binding components of the hepatic microsomes were partly solubilized by treatment with the detergent Triton X-100. These solubilized progesterone binding components were progesterone saturable ( K a ∼ 3 × 10 7M −1) and specific for progesterone. Of the 11 steroids tested progesterone showed the highest competition for microsome-bound [ 3H]-progesterone. The progesterone binding capacity of female rat liver microsomes was decreased after protease and RNase treatment, suggesting that both protein and RNA were involved, directly or indirectly, in progesterone binding to the microsomes. Treatment of the liver mierosomes with EDTA (0–17 mM) or KC1 (0.4 M) had no effect on the binding of progesterone. The microsomal suspensions of rat liver resisted freezing without loss of their progesterone binding activity, whereas approximately one half of their progesterone binding capacity was lost after incubation at +37°C for 15 min.

Aryl hydrocarbon (benzo[a]pyrene) hydroxylases in liver from rats of different age, sex and nutritional status: Distinction of two types by 7,8-benzoflavone

Two types of aryl hydrocarbon (benzo[a]pyrene) hydroxylase have been distinguished in liver from rats of different sex and age by their sensitivity to the synthetic flavonoid, 7,8-benzoflavone. One type, which is stimulated by the 7,8-benzoflavone, is found in newborn rats and predominates in the liver of adult male rats. This type is inducible by phenobarbital. A second type, which is inhibited by 7,8-benzoflavone, comprises a larger fraction in the liver of adult female rats and is inducible by polycyclic hydrocarbons in immature and mature animals of either sex. The presence of this form in adult female liver is also indicated by the kinetics of the hydroxylase reaction. Removal of solid food for 18 hr not only decreases hepatic aryl hydrocarbon hydroxylase activity in female rats, but also lowers the degree of inhibition by 7,8-benzoflavone. Kinetic data suggest that at low concentrations 7,8-benzoflavone acts as a competitive inhibitor but at higher concentrations inhibits the hydroxylation reaction by a more complex mechanism.

Prolactin Receptors in Rat Liver: Possible Induction by Prolactin

A prolactin receptor, present in adult female rat liver, can be induced in males by estrogen. Hypophysectomy diminished receptor levels in the female and rendered males unresponsive to estrogen. A renal pituitary implant blunted the decrease in hypophysectomized females and induced the receptor in hyophysectomized males. The increased receptor level in hypophysectomized males with a renal pituitary implant was preceded by a sustained elevation of circulating prolactin. Our observations suggest that prolactin induces its own receptor.

Testosterone delta 4-reductase activity in rat liver: hormonal control in vivo.

SUMMARY The rate-limiting step in the metabolism of testosterone by the liver is reduction of the double bond in ring A. Using a spectrophotometric assay we have studied the effects of some hormonal manipulations on the levels (per mg protein) of testosterone Δ4-reductase activity in rat liver. While the levels of enzyme activity were higher for adult female rat liver than for adult male liver, there were no further changes in livers from female rats at day 15 of gestation. In male rats, castration increased, hypophysectomy decreased and adrenalectomy had no effect on the level of activity. Administration of oestradiol valerate increased the activity in intact and adrenalectomized animals and had no effect in the hypophysectomized or castrated groups. Administration of testosterone enanthate decreased the levels of activity in the castrated and adrenalectomized groups and had no effects in unoperated or hypophysectomized animals. When given together, the two hormones were antagonistic. Prolactin had no significant effects in either intact or hypophysectomized animals. Experiments with actinomycin D and cycloheximide indicated that the synthesis of new protein was involved in the effects of oestradiol in intact rats. All the changes reflected alterations in the microsomal enzyme level.

Radioactivity in Reproductive Organs and the Liver of Neonatal and Adult Rats Following <sup>3</sup>H-Testosterone Administration

The uptake of radioactivity by the reproductive organs and livers of neonatal, prepuberal, puberal and adult male and female rats 1 h after intraperitoneal administration of <sup>3</sup>H-testosterone was measured by liquid scintillation quantification. Tissue homogenates of the testes, vasa deferentia-epididymides, ovaries, uteri, livers, muscle, cerebrum and thymuses were fractionated and aqueous, lipid and protein-nucleoprotein fractions separated for analysis. Accumulation of radioactivity above control levels was found in all fractions of the tissues, particularly in the fractions containing the protein-nucleoprotein residues of the reproductive organs and livers. The radioactivities associated with the tissue residues of reproductive organs were highest during the first postnatal days and subsequently declined while the radioactivities associated with the livers were lowest 2 days after birth and increased markedly by day 10. These observations suggest that the alterations in sexual physiology and behavior observed in adult female rats subsequent to administration of androgens during their neonatal critical period of sex development may be due to immaturity of steroid degradative mechanisms in the neonatal liver.

Phospholipid metabolism in the developing liver: I. The biosynthesis of choline glycerophosphatides by liver slices from fetal, newborn and adult rats

1. 1. The biosynthesis of choline glycerophosphatides was evaluated in fetal, neonatal and adult female rat liver. The two main pathways were assessed by studying the rates of incorporation of [ Me- 14C]choline and [ Me- 14C]methionine by liver slices. 2. 2. Over 96% of the lipid radioactivity from [ Me- 14C] choline was located in choline glycerophosphatides. In adult liver slices 93% of the total lipid radioactivity from [ Me- 14C]methionine was located in choline glycerophosphatides. An appreciable amount of radioactivity from [ Me- 14C]methionine was incorporated into fatty acids by fetal liver slices. 3. 3. Liver slices from fetal rats incorporated the same amount of [ Me- 14C]choline into lecithin as did adult liver slices except for a drop 2 days before birth. Liver slices from 3-day-old neonatal rats incorporated about twice as much [ Me- 14C]choline as the adult liver slices. 4. 4. Liver slices from fetal and young rats incorporated about 8–10 times more [ Me- 14C]choline into phosphoryl choline than did liver slices from adults. Adult levels were reached at 10 days after birth. 5. 5. The incorporation of radioactivity from [ Me- 14C]methionine into lecithin by fetal liver slices was much lower than that by adult liver slices and increased to twice adult levels by 10–12 days after birth. Adult levels were reached by 25 days after birth. 6. 6. Studies with [1,2- 14C 2, Me- 14H]choline indicated that the choline was incorporated intact and that little, if any, of the methyl groups of choline were used for the methylation of phosphatidyl ethanolamine. 7. 7. The mechanism of choline incorporation into lecithin is discussed.

Metabolic and electrophoretic studies of rat liver sorbitol dehydrogenase.

The effect of various factors on the activity of rat liver sorbitol dehydrogenase was investigated. The activity of the enzyme (expressed per gram of tissue) was similar in the livers of adult male and female rats and was not affected by adrenalectomy, cortisone injection, or hypophysectomy. Different modes of administration of sorbitol also produced little change in activity. The enzyme activity declined significantly during 1 week of starvation. Activity was low in foetal liver and rose gradually during the postnatal period to reach adult levels by approximately 40 days after birth. Sorbitol dehydrogenase activity in the moderately well-differentiated Morris hepatoma 5123 T.C. was studied and found to be approximately 40% of that of normal liver. Using the technique of starch-gel electrophoresis in sodium borate, the rat liver enzyme was found to occur in multiple molecular forms. The electrophoretic pattern of the rat liver enzyme in sodium borate was not affected by a variety of metabolic conditions and was also identical in the hepatoma. From a study of various factors influencing the electrophoretic separation of rat liver sorbitol dehydrogenase, it is concluded that the multiple molecular forms are similar species of the enzyme and that interaction with a starch–borate complex may be important in their resolution.

Partial characterization of the RNA stimulating growth of the seminal vesicle.

RNA prepared from the seminal vesicles of intact adult rats, or of testosterone-treated castrate adult rats, produced a 30 per cent increase in the weight of the seminal vesicle and a 25 per cent increase in the incorporation of labeled amino acids into protein. RNA prepared from the liver or ventral prostate of the same animals produced only a 10 per cent increase in the weight of the seminal vesicle. RNA prepared from the liver of control or testosterone-treated adult female rats was ineffective in stimulating the growth of the seminal vesicle. Polyuridylic acid instilled into the lumen had no effect on the weight of the seminal vesicle, but increased the incorporation of labeled phenylalanine into protein. RNA sedimenting in the 18S area on sucrose density gradients was most effective in stimulating growth of the seminal vesicle of three-week-old rats. Treating homogenized tissue with deoxycholate greatly increased the effectiveness of the RNA extracted. RNA extracted from seminal vesicles by treatment with deoxycholate and dextran sulfate was biologically active, whereas the usual 4S RNA in the 100,000 x g supernatant is ineffective.

The ferritin content of the free ribosome fraction isolated from adult male and female rat liver

The ferritin content of the free ribosome fraction isolated from adult male and female rat liver

Dehydroxylation and deacetylation of N-hydroxy- N-2-fluorenylacetamide by rat liver and brain homogenates

Two reactions, dehydroxylation and deacetylation of the proximate carcinogen N-hydroxy- N-2-fluorenylacetamide were studied with liver and brain homogenates, or with a soluble fraction from liver of young or adult male or female rats of two strains. Incubation of N-hydroxy- N-2-[9- 14 C]fluorenylacetamide with tissue homogenate in 0.2 M Tris buffer (pH 8.1) gave progressively decreasing levels of substrate. The products, N-2-fluorenylacetamide and 2-fluorenamine, were resolved and identified by solvent partition, paper chromatography, ultraviolet spectroscopy, and color tests. Liver homogenate from 2 rat strains was most active, the soluble liver fraction slightly less so, and brain homogenate least. Deacetylation was but dehyroxylation was not inhibited by 0.1 M fluoride. Both reactions proceeded equally well in nitrogen or in air. The dehydroxylase was inactive after 1 h at 37°. The decaylase was somewhat more stable. Linear increases in protein-binding of 14C from the substrate were found. The final level was lower in liver from adult female rats than from males, but was similar with weanling rats. Binding was inhibited somewhat by fluoride and more so by a nitrogen atmosphere. Some of the binding may have been due to the oxidation of amine or hydroxylamine in the presence of tissue. Isotope from synthetic N-2-[ 14C] fluorenylhydroxylamine and 2-nitroso[9 −14C]fluorene bound to serum proteins, liver homogenate or soluble liver fractions, hemoglobin, albumin, γ-globulin, or histones. 2-Nitrosofluorene reacted similarly in air and in nitrogen. It may be the active intermediate.