Significance of experimental studies for assessing adverse effects of endocrine-disrupting chemicals

2003 ◽  
Vol 75 (11-12) ◽  
pp. 2125-2141 ◽  
Author(s):  
L. E. Gray ◽  
P. M. D. Foster
Keyword(s):  
Adverse Effects ◽  
Statistical Power ◽  
Experimental Studies ◽  
Male Rats ◽  
Male Rat ◽  
High Dose ◽  
Tier 2 ◽  
In Vivo Assays ◽  
Endocrine Disrupting

The U.S. Environmental Protection Agency (USEPA) is developing an endocrine disruptor screening and testing program to detect chemicals that alter hypothalamic-pituitary-gonadal (HPG) function, estrogen, androgen, and thyroid (EAT) hormone synthesis or metabolism and induce androgen (AR) and estrogen (ER) receptor-mediated effects in mammals and other animals. The utility of this approach is based upon the knowledge that mechanisms of endocrine-disrupting chemical (EDC) action are highly conserved at the cellular and molecular levels among vertebrates. Some EDC mechanisms also are shared with invertebrates. High-priority chemicals would be evaluated in a Tier 1 screening (T1S) battery, and chemicals that are positive in T1S would then be tested in Tier 2 (T2). T1S includes in vitro ER and AR receptor binding and/or gene expression, an assessment of steroidogenesis and mammalian (rat) and nonmammalian (fish) in vivo assays. In vivo, the uterotropic assay detects estrogens and antiestrogens, while steroidogenesis, antithyroid activity, antiestrogenicity, and HPG function are assessed in a pubertal female assay. Antiandrogens are detected in the Hershberger assay (weight of androgen-dependent tissues in castrate-immature-male rats). Fish and amphibian assays are also being developed to identify EDCs. Several alternative mammalian in vivo assays have been proposed. Of these, a short-term pubertal male rat assay appears most promising. T1S is designed to be sensitive to EAT activities, but many of the effects detected at the screening level would not be considered adverse, the dosage levels may be high, and the route of administration used may not be the most relevant. However, issues of adversity, dose response, and route(s) of exposure would be resolved in the testing phase. In addition to using an enhanced multigenerational test for Tier 2, an in utero-lactational screening protocol is also being evaluated by USEPA for use in T2 or T1S. For T2, the numbers of endocrine-sensitive end-points and offspring (F1) examined in multigenerational tests need to be expanded for EDCs in a thoughtful manner, based in part upon the results of T1S. In addition, for some chemicals histological examination of 10 adult F1 per sex in only the control and high-dose groups provides inadequate statistical power to detect low-dose lesions induced during development. In these cases, we propose that all the offspring be examined after puberty for gross and histological reproductive abnormalities. Since EDCs, like the phthalates and AR-antagonists, produce characteristic profiles, or syndromes, of adverse effects, data need to be reported in a manner that clearly identifies the proportion of animals displaying one or more of the abnormalities in a syndrome. Consideration should be given to tailoring T2, based on the results of T1S to assure that all of the effects in such chemically induced developmental syndromes are included in the study.

In-vivo uptake of human growth hormone in male rat liver

1989 ◽  
Vol 121 (1) ◽  
pp. 19-25 ◽  
Author(s):  
F. Bullier-Picard ◽  
M. C. Postel-Vinay ◽  
C. Kayser
Keyword(s):  
Plasma Membranes ◽  
Human Growth ◽  
Rat Hepatocytes ◽  
Male Rats ◽  
Male Rat ◽  
Liver Homogenates ◽  
Isopycnic Centrifugation ◽  
Specific Labelling ◽  
In Vivo Uptake

ABSTRACT 125I-Labelled human GH (hGH) was injected i.v. to male rats and its subcellular distribution in the hepatocyte was examined using fractionation techniques. Uptake into liver homogenates was maximal by 15 min after injection and represented 24% of the injected radioactivity; it was markedly inhibited by coinjection of native hGH. 125I-Labelled hGH taken up by the liver underwent a time-dependent translocation process. The peak of specific labelling of plasma membranes occurred at 3 min whereas later on the radioactivity was concentrated in low-density structures present in Golgi-endosome fractions. To characterize the ligand-associated structures better, endosome-enriched fractions were prepared from a microsomal fraction by isopycnic centrifugation in a sucrose gradient and a Nycodenz gradient. The radioactivity was in one peak with a median density of 1·096 g/cm3 in the Nycodenz gradient fractions. The peak of radioactivity was distinct from that of galactosyltransferase activity which appeared at a median density of 1·114 g/cm3. The labelled material eluted from the various subcellular fractions appeared as intact hGH. Upon in-vivo interaction with male rat hepatocytes, 125I-labelled hGH was internalized with a sequential association with plasma membranes and endocytic structures distinct from Golgi elements. Journal of Endocrinology (1989) 121, 19–25

The Effects of Jp-8 Jet Fuel on Male Sprague-Dawley Rats after a 90-Day Exposure By Oral Gavage

1995 ◽  
Vol 11 (4) ◽  
pp. 423-435 ◽  
Author(s):  
David R. Mattie ◽  
Gary B. Marit ◽  
Carlyle D. Flemming ◽  
James R. Cooper
Keyword(s):  
Adverse Effects ◽  
Jet Fuel ◽  
Additional Treatment ◽  
Male Rats ◽  
Male Rat ◽  
Oral Exposure ◽  
Sprague Dawley ◽  
Weight Changes ◽  
Inhalation Study ◽  
Dose Dependent

The U.S. Air Force is converting from JP-4 jet fuel to the less volatile JP-8 jet fuel, which is similar to commercial Jet Fuel A. Our previous 90-day inhalation study with JP-8 vapor, using F-344 rats and C57BL/6 mice, resulted in no treatment-related adverse effects other than α 2-microglobin nephropathy in male rats (Mattie et al., 1991). In the present study, male rats were dosed with neat JP-8 (0, 750, 1500, 3000 mg/kg) daily by gavage for 90 days in an effort to characterize the kidney lesion and assess further any additional adverse effects associated with prolonged oral exposure to this fuel. Results of this study revealed a significant dose-dependent decrease in body weights of rats exposed to JP-8. Male rat-specific α 2-microglobin nephropathy was observed by histopathologic examination. A number of significant changes were also seen in blood and urine that were not dose-dependent. Additional treatment-related effects were a gastritis and a perianal dermatitis. Although there were no histopathological or weight changes in the livers of exposed rats, there was an increase in the liver enzymes AST and ALT. The elevated enzymes did not increase with increasing dose of JP-8.

ACTIONS OF CATECHOL OESTROGENS ON CONCENTRATIONS OF SERUM LUTEINIZING HORMONE IN THE ADULT CASTRATED RAT: VARIOUS EFFECTS OF 4-HYDROXYOESTRADIOL AND 2-HYDROXYOESTRADIOL

1981 ◽  
Vol 89 (2) ◽  
pp. 289-295 ◽  
Author(s):  
S. FRANKS ◽  
N. J. MacLUSKY ◽  
S. J. NAISH ◽  
F. NAFTOLIN
Keyword(s):  
Serum Levels ◽  
Male Rats ◽  
Hydroxyl Group ◽  
High Dose ◽  
Binding Properties ◽  
Potent Effect ◽  
Naturally Occurring ◽  
Serum Luteinizing Hormone ◽  
The Right

The pharmacological effect of 2-hydroxyoestradiol (2-OHE2) and 4-OHE2 on concentrations of LH in the chronically castrated rat have been compared with that of oestradiol in order to determine whether the in-vivo activity is altered by insertion of a hydroxyl group at position 2 or 4 of the aromatic A ring; these derivatives are naturally occurring oestrogen metabolites. Four groups of six adult male rats were used 4 weeks after bilateral orchidectomy. The right jugular vein was exposed under ether anaesthesia and a basal blood sample taken (10.00 h) immediately before an intravenous injection of vehicle alone (0·1 ml ethanol with 0·01 % ascorbic acid), oestradiol, 2-OHE2 or 4-OHE2 (10 μg of each in 0·1 ml vehicle). Blood was taken from each animal at 2, 4, 6, 8 and 24 h after treatment and serum assayed for LH. Baseline LH levels were similar in the four groups. At 2 h there was no change in 2-OHE2-treated rats but there was a significant decrease of serum levels of LH in rats treated with oestradiol and 4-OHE2 compared with vehicle-treated controls. The decrease in LH was quantitatively similar in oestradiol- and 4-OHE2-treated groups and was sustained at 4, 6 and 8 h, returning to control values at 24 h. In subsequent experiments the effects of lower doses of these two steroids were compared and the potency of 4-OHE2 was estimated to be about 25% that of oestradiol. In a further experiment, 2-OHE2 (100 μg) had no effect when given alone, but when injected i.v. immediately before treatment with 1 μg oestradiol, it was able to inhibit the suppression of LH by oestradiol. In conclusion, 4-OHE2 had a potent effect in lowering plasma LH levels whereas 2-OHE2, even at a high dose (100 μg), did not suppress LH but it was able to inhibit the effect of oestradiol. These differences in biological activity may reflect more rapid metabolism of 2-OHE2 or differences in binding properties of these catechol oestrogens to the oestrogen receptor.

Quantification of the Uncertainties in Extrapolating From In Vitro Androgen Receptor Antagonism to In Vivo Hershberger Assay Endpoints and Adverse Reproductive Development in Male Rats

2020 ◽  
Vol 176 (2) ◽  
pp. 297-311
Author(s):  
Leon E Gray ◽  
Johnathan R Furr ◽  
Christy S Lambright ◽  
Nicola Evans ◽  
Phillip C Hartig ◽  
...  
Keyword(s):  
Androgen Receptor ◽  
Adverse Outcome ◽  
In Utero ◽  
Male Rats ◽  
Male Rat ◽  
Rat Offspring ◽  
Hershberger Assay ◽  
Key Events

Abstract Multiple molecular initiating events exist that disrupt male sexual differentiation in utero including androgen receptor (AR) antagonism and inhibition of synthesis, and metabolism of fetal testosterone. Disruption of androgen signaling by AR antagonists in utero reduces anogenital distance (AGD) and induces malformations in F1 male rat offspring. We are developing a quantitative network of adverse outcome pathways that includes multiple molecular initiating events and key events linking anti-AR activities to permanent reproductive abnormalities. Here, our objective was to determine how accurately the EC50s for AR antagonism in vitro or ED50s for reduced tissue growth in the Hershberger assay (HA) (key events in the adverse outcome pathway) predict the ED50s for reduced AGD in male rats exposed in utero to AR antagonists. This effort included in-house data and published studies from the last 60 years on AR antagonism in vitro and in vivo effects in the HA and on AGD after in utero exposure. In total, more than 250 studies were selected and included in the analysis with data from about 60 potentially antiandrogenic chemicals. The ability to predict ED50s for key events and adverse developmental effects from the in vitro EC50s displays considerable uncertainty with R2 values for HA and AGD of < 6%. In contrast, there is considerably less uncertainty in extrapolating from the ED50s in the HA to the ED50s for AGD (R2 value of about 85%). In summary, the current results suggest that the key events measured in the HA can be extrapolated with reasonable certainty to predict the ED50s for the adverse in utero effects of antiandrogenic chemicals on male rat offspring.

Echinochrome Pigment Improves Male Rats' Fertility

2020 ◽  
Vol 10 ◽  
Author(s):  
Neveen Asmet Farag ◽  
Ayman S Mohamed ◽  
Hanan Farag El Sayed ◽  
Eman Y. Salah EL-Din ◽  
Abdel Rahman A. Tawfik
Keyword(s):  
Sperm Count ◽  
Significant Proportion ◽  
Married Couples ◽  
Testicular Tissue ◽  
Significant Rise ◽  
Male Rats ◽  
Male Rat ◽  
High Dose ◽  
Testis Weight ◽  
Positive Effect

Background:: Infertility is the first-rate public health trouble affecting one in five married couples globally, male causes embody a significant proportion. Natural products could be an alternative or complementary inexpensive treatment for such matters. Echinochrome (Ech) is a natural quinone pigment obtained from sea urchin, and it was confirmed to possess many pharmacological properties due to its chemical activity. Objective:: The current research paper was targeted to evaluate the potential effects of Ech on male fertility, and to highlight the possible involved mechanisms. Methods:: Eighteen adult male rats were randomly distributed into three groups: control (1 ml of 2% DMSO, p.o.), low dose Ech (0.1 mg/kg, p.o.), and high dose Ech (1 mg/kg p.o.). Results:: The high dose Ech caused a significant decline in the levels of glucose, ALT, AST, ALP, urea, Cr, uric acid, TG, TC and LDL-C and testicular tissue MDA, while it caused a significant rise in the levels of albumin, TP, HDL-C, FSH, LH, testosterone and testicular tissue GSH activity. Moreover, it showed a significant positive effect on the testis weight, caudal epididymis weight, sperm count, sperm motility, sperm morphology, fructose concentration, and α-glucosidase activity. However, no significant changes were observed in histological examination of testicular tissue among all groups. Conclusion:: High dose Ech improved male rat-fertility either directly by activating the pituitary gonadal axis, and or indirectly via enhancing: the renal and hepatic functions, the lipid profile and or the antioxidant pathways.

AN AUTORADIOGRAPHIC STUDY ON THE LOCALIZATION OF ANDROGEN IN THE PROSTATE GLAND AND THE SEMINAL VESICLES OF THE MALE RAT

1970 ◽  
Vol 63 (2) ◽  
pp. 207-215 ◽  
Author(s):  
Kjell J. Tveter
Keyword(s):  
Epithelial Cells ◽  
Prostate Gland ◽  
Autoradiographic Study ◽  
Seminal Vesicles ◽  
Radioactive Material ◽  
Male Rats ◽  
Male Rat ◽  
Selective Localization ◽  
Qualitative Pattern

ABSTRACT The distribution of radioactive material in the prostate gland and the seminal vesicles has been studied by autoradiography after intramuscular administration of [1,2-3H] testosterone in vivo to adult castrated male rats. Positive autoradiographs were obtained from 7½ min to 8 h after the administration. As early as after 15 min, there appeared to be a selective localization of radioactivity in the epithelial cells, with much of the labelling associated with the nuclei; the stromal labelling was markedly less. This picture was even more significant ½, 1 and 2 h after the injection, when the autoradiographs demonstrated a preferential labelling of the nuclei of the epithelial cells. A distinct labelling of the epithelial cells was also found 8 h after the injection. The same qualitative pattern of distribution of radioactivity was seen in the four prostatic lobes and the seminal vesicles. No significant labelling of the secretions in the glandular lumina was observed.

EXPERIMENTAL EVALUATION OF DIURETICS IN THE RAT

1956 ◽  
Vol 34 (1) ◽  
pp. 903-911
Author(s):  
J. D. McColl ◽  
J. M. Parker ◽  
J. K.W. Ferguson
Keyword(s):  
Carbonic Anhydrase ◽  
Dose Range ◽  
Carbonic Anhydrase Inhibitor ◽  
Female Rats ◽  
Male Rats ◽  
Male Rat ◽  
High Dose ◽  
Female Rat ◽  
Inhibitor Type ◽  
Almost All

The diuretic response of the male and the female rat to aminophylline has been studied when these animals were pretreated with various concentrations of sodium chloride solution. A linear log dose – response curve was obtained over the dose range employed with male rats pretreated with 0.45% and 2% saline. Male rats exhibited a diuresis with 4% saline which was not increased by aminophylline. Female rats showed diuresis but the responses were more variable for almost all combinations of electrolyte load and xanthine dose. When they were pretreated with 0.45% and 2% saline, aminophylline caused some additional production of urine but this was much less regular than that observed with males. The variation in response to aminophylline after 4% saline was very marked but the trend suggested that the xanthine had a diuretic effect at the high dose. The diuretic responses to a xanthine, a mercurial, and a carbonic anhydrase inhibitor type of diuretic were compared in the male rat. Peak responses were smallest after the mercurial diuretic and greatest with the carbonic anhydrase inhibitor.

AN EXPERIMENTAL ANALYSIS OF THE EFFECTS OF OESTROGEN ON THE THYROID GLAND OF CASTRATED ADULT MALE RATS

1968 ◽  
Vol 40 (4) ◽  
pp. 397-408 ◽  
Author(s):  
J. F. BITHELL ◽  
K. BROWN-GRANT
Keyword(s):  
Thyroid Gland ◽  
Rate Constant ◽  
Adult Male ◽  
Time Course ◽  
Hormone Secretion ◽  
Male Rats ◽  
Male Rat ◽  
Exit Rate ◽  
Experimental Conditions

SUMMARY The uptake of 131I by the thyroid gland of the castrated adult male rat is increased 24 hr. and is maximal 48 hr. after the injection of a single dose of 50 μg. oestradiol. The response is not dose-dependent between 25 and 1600 μg. The thyroid:serum (T:S) concentration ratio for 131I is also increased by oestradiol with a time-course similar to the changes in uptake, but release of 131I-labelled hormone from the gland in vivo and radioactive phosphate uptake were not affected. Analysis of the kinetics of 131I accumulation by the blocked gland show that the effects on 131I uptake and T:S ratio were due to an increase in the clearance rate with a possible associated decrease in the exit rate constant for iodide from the gland to the blood. Under the conditions of these experiments, the effects of oestradiol are not consistent with their being produced by an increase in pituitary thyrotrophic hormone secretion; a direct action on the gland appears likely. These conclusions apply solely to the experimental conditions described here and do not provide the basis for any generalization about the action of oestrogens on the thyroid gland. The method of analysis developed for the estimation of the unilateral clearance constant and the exit rate constant, together with their standard deviations, is presented in an appendix.

scholarly journals Inhibition of cyclo-oxigenase-2 activity does not abolish the anabolic effect of prostaglandin E2 in vivo or in vitro

2002 ◽  
Vol 174 (1) ◽  
pp. 127-135 ◽  
Author(s):  
M Weinreb ◽  
A Kelner ◽  
S Keila
Keyword(s):  
Bone Formation ◽  
Bone Tissue ◽  
Receptor Expression ◽  
Male Rats ◽  
Nodule Formation ◽  
High Dose ◽  
Anabolic Effect ◽  
Cox 2

It was previously reported that the expression of cyclo-oxigenase-2 (COX-2) is induced by prostaglandin E(2) (PGE(2)) in vitro in an osteogenic cell line and organ culture, suggesting an autoamplification mechanism. In this study, we first tested whether this phenomenon also occurs in bone tissue in vivo and found that a single anabolic dose of PGE(2) (5 mg/kg) induced (between 30 and 120 min) in rat tibiae, an increase in the mRNA level of COX-2 (2.5- to 9-fold) but not that of COX-1. Secondly, to test whether COX-2 activity in generating endogenous prostaglandins (PGs) is required for the in vivo anabolic properties of PGE(2), young male rats were injected daily with either vehicle (8% ethanol) or 5 mg/kg PGE(2) for 21 days. PGE(2)-injected rats received, 45 min prior to PGE(2), either dimethyl sulphoxide (as vehicle) or one of two doses of NS-398, a selective COX-2 inhibitor: a low dose (3 mg/kg) or a high dose (10 mg/kg). PGE(2) increased bone formation (measured as cancellous mineralizing surface, mineral apposition rate and bone formation rate) and bone mass (measured as cancellous bone area and surface and cortical width). None of these increases was suppressed by pre-administration of NS-398. In contrast, the high dose of NS-398 effectively suppressed an increase in rat hind-paw volume induced by a local carrageenan injection. Furthermore, since COX-2 inactivation may affect PG receptor expression, we found that pre-administration of NS-398 did not abolish the induction in EP(4) receptor mRNA levels, caused by PGE(2) in rat bone tissue. For in vitro testing, rat femoral bone marrow stromal cell cultures were initiated and were incubated in the absence or presence of PGE(2) at 100 nM (as an inducer) and with increasing concentrations of NS-398 (10(-8) M to 10(-5) M) for 21 days, after which time mineralized (Von-Kossa positive) nodules were counted. PGE(2) increased nodule formation as previously reported; however, NS-398 reduced nodule formation in both control and PGE(2)-treated cultures to the same extent. We conclude that while the level of COX-2 mRNA is increased in vivo by administration of PGE(2), inhibition of its activity (i.e. generation of endogenous PGs) does not abolish the anabolic effect of PGE(2).

Effects of Mannitol and Iohexol Infusions on the Renal Cortical Blood Flow in Dehydrated Mice

1996 ◽  
Vol 37 (3P2) ◽  
pp. 591-595 ◽  
Author(s):  
B. Högström ◽  
S.-O. Hietala ◽  
P. Rooth
Keyword(s):  
Blood Flow ◽  
Adverse Effects ◽  
Fluorescence Microscopy ◽  
Contrast Medium ◽  
Experimental Studies ◽  
Cortical Blood Flow ◽  
In Vivo Fluorescence ◽  
Renal Cortical Blood Flow ◽  
Increased Blood Flow

In vivo fluorescence microscopy was used in experimental studies of renal cortical microcirculation in mice. The effects of intravenous infusions of equimolar concentrations of mannitol and iohexol were studied in normal lean mice and obese/hyperglycemic mice after dehydration overnight. All infusions produced marked effects in distribution and velocity of renal cortical blood flow. Initially increased blood flow was seen in a number of capillaries after infusion of both mannitol and iohexol, and renal cortical blood flow was inhomogeneous for different capillaries. A significantly (p<0.05) larger number of capillaries with decreased blood flow, within the first minutes after start of infusion, was observed after infusion of iohexol to normal mice when the animals had been dehydrated overnight. Our results indicate that the minor adverse effects on renal cortical blood flow caused by the infusion of contrast medium are potentiated by dehydration.

Sign in / Sign up

Export Citation Format

Share Document