Neural correlates of species-typical behavior in the Syrian golden hamster.

The behavior of a total of 84 Syrian golden hamsters with lesions to the medial frontal cortex (MF), orbital frontal cortex (OF), cingulate cortex (CING), posterior cortex (POST), hippocampus (HPC), septum (SEPT), or amygdala (AMYG) was compared with that of 12 control hamsters in a variety of situations, including weight regulation, food hoarding, nest building, neophobia, bait shyness, sex preference, territorial aggression, and shock-induced aggression. The behavior of Ss with OF or AMYG lesions was doubly dissociable from the behavior of Ss with MF, HPC, or SEPT lesions. The OF and AMYG lesions produced severe weight losses, and all OF Ss were aphagic and adipsic and subsequently died. The HPC, MF, and SEPT lesions severely disrupted hoarding and nest building, whereas the other lesions affected neither. None of the lesions impaired the development of bait shyness when a sucrose solution was paired with sickness, but both AMYG and SEPT lesions may have produced a mild impairment when an NaCl solution was paired with sickness. Only amygdala lesions produced consistent behavioral changes on the social tests. Neither cingulate nor posterior cortical lesions significantly altered behavior on any of the tests. Results support the idea that different forebrain regions can be functionally dissociated by using behavioral tests that are biologically significant. (56 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of glutathione and cysteine conjugates in the nephrotoxicity of o-xylene in rats

One-hundred-eighty cylindrical monocortical titanium implants, 4mm diameter and 12mm long, with three different coatings: fluorohydroxyapatite (group A), hydroxyapatite (group B), and titanium oxide (group C), all applied by vacuum plasma spray were bilaterally, randomly implanted into the femurs and tibiae of twelve adult mongrel sheep. The sheep were divided into four groups (1, 2, 3 and 4) numbering three sheep each. Sheep of groups 1, 2, 3 and 4 were euthanized at two weeks, one month, three and nine months after implantation, respectively Biomechanical and histomorphological analysis were performed. Extraction torque increased over time in all groups until the nine months period. At all the studied periods, the bone-implant contact was higher in Groups A and B compared to Group C. However, only at nine months did this difference reach statistical significance (p<0.005 comparing Groups A and B to C). The results of this study show that all the three coatings could be recommended for clinical applications.     

Comparative ultrastructure of vallate, foliate and fungiform taste buds of golden Syrian hamster

A fine-structure study of the hamster fungiform, foliate and vallate taste buds was undertaken for comparative purposes. All three taste bud types shared in common composition of the dark cells, light cells, basal cells, nerve fibers and nerve endings and undifferentiated peripheral cells, but morphological difference existed among them. The foliate and vallate taste buds were quite similar in their ultrastructural morphology. Their dark cells displayed long apical necks, long apical microvilli, apical osmiophilic secretory granules and an abundant rough endoplasmic reticulum. The dark cells of the fungiform taste buds, however, showed no neck formation and lacked apical osmiophilic granules. They had short apical microvilli and relatively scant rough endoplasmic reticulum. There was no difference in the fine structure features of the light cells, basal cells and neural elements of different types of taste buds. Both light and dark cells were much more readily distinguishable in foliate and vallate buds than in fungiform buds at both light-and electron-microscopic levels. Foliate and vallate buds demonstrated homogeneous dense substance within the taste pores while fungiform pores were frequently empty. It is speculated that the differences in taste bud morphology may be due to their different lingual locations and/or may be a reflection of the differences in the inductive influences from different nerves. Furthermore, structural differences may be responsible for varying thresholds to different taste modalities.     

Formation of glutathione conjugates of prostaglandin A1 in human red blood cells

When prostaglandin A1 was incubated with a Tris/saline suspension of washed human red blood cells, a substantial amount was converted to polar metabolites. These were purified by solvent extraction, XAD-2 column, and cellulose thin layer chromatography and characterized by chromatography, amino acid analysis, and mass spectrometry. The polar metabolites were a mixture of two glutathione conjugates of prostaglandin A1. The first (approximately 40%) was identical with the product of the nonenzymic reaction of glutathione with prostaglandin A1. The second (approximately 60%) was formed from the first by reduction of the 9-keto group of the prostaglandin moiety. The latter compound was also prepared synthetically by treating the glutathione conjugate of prostaglandin A1 with sodium borohydride.     

Investigation of epididymal sperm maturation in the golden hamster

During passage of hamster spermatozoa through the epididymis their maturation is shown to involve changes in the sperm head, midpiece (mitochondria) and tail. The sum of these changes results in a dramatic increase in the fertilizing potential of the spermatozoa. When comparable numbers of spermatozoa from the caput or corpus epididymis were injected into one uterine horn of mature females, following ovulation induction, and spermatozoa from the cauda epididymis were injected into the contralateral horn, no fertilization was observed with caput epididymal spermatozoa, 1.7% of oocytes were fertilized by corpus epididymal spermatozoa, whereas 79.5% fertilization was obtained with cauda epididymal spermatozoa. Total sperm numbers increased from caput to corpus to cauda [28.3 +/- 12.2, 40.6 +/- 20.8, 144 [corrected] +/- 62 million, respectively]. The percentage of progressively motile spermatozoa increased from 27.9 +/- 6.4 to 33.8 +/- 4.8 to 70 +/- 10.7 during this passage. Viability, measured by exclusion of the dye, propidium iodide, was significantly less in spermatozoa from the cauda than from the proximal or mid-caput epididymis. The percentage of the live cells that were stained intensely by rhodamine-123 (a measure of mitochondrial membrane potential) increased during epididymal passage from 22.8 +/- 7.8% in the proximal caput epididymis to 57.2 +/- 16.5% in the cauda epididymis. Staining with acridine orange (a measure of DNA packaging in the sperm head) indicated an increase in chromatin condensation in cauda epididymal spermatozoa, when compared to those obtained from the caput or corpus.     

The lumbar cord location of the motoneurons innervating psoas and iliacus muscles: a single and double labeling study in the female Syrian golden hamster

The spinal cord location of the motoneurons innervating the psoas and iliacus muscles was determined in the golden hamster. The results of single and double labeling studies, using the retrograde tracers horseradish peroxidase (HRP) and cholera toxin B-subunit (CTB), showed that both psoas and iliacus motoneurons were present ventrolaterally in the ventral horn in the caudal L1 to rostral L5 lumbar spinal segments with their motoneurons intermingled in one cell group. Further retrograde tracing studies demonstrated abdominal muscle motoneurons ventrolaterally in the ventral horn of the L1 and upper L2 segments. Double labeling experiments revealed that at these levels (caudal L1 and rostral L2), the abdominal muscle motoneurons were located dorsomedial to the psoas and iliacus motoneurons.     

Increased compliance in diaphragm muscle of the cardiomyopathic Syrian hamster

We investigated the hypothesis that diaphragm compliance was abnormal in cardiomyopathic Syrian hamsters (CSH), an experimental model of myopathy. The passive elastic properties of isolated diaphragm muscles were analyzed at both the muscle and sarcomere levels. We used the following passive exponential relationship between stress (sigma) and strain (epsilon): sigma = (Eo/beta) (ebetaepsilon - 1), where Eo is the initial elastic modulus and beta is the stiffness constant. Immunocytochemistry procedures were used to analyze the distribution of two key elastic components of muscle, extracellular collagen and intracellular titin elastic components, as well as the extracellular matrix glycoprotein laminin. Muscle and sarcomere values of beta were nearly twofold lower in CSH (8.7 +/- 1.9 and 8.3 +/- 1.4, respectively) than in control animals (19.7 +/- 1.7 and 16.8 +/- 2.1, respectively) (P < 0.01 for each). Compared with controls, Eo was higher in CSH. Sarcomere slack length was significantly longer in CSH than in control animals (2.1 +/- 0.1 vs. 1.9 +/- 0.1 micrometer, P < 0.05). The surface area of collagen I was significantly larger in CSH (17.4 +/- 1.8%) than in control animals (12.4 +/- 0.7%, P < 0.05). There was no change in the distribution of titin or laminin labelings between the groups. These results demonstrate increased diaphragm compliance in cardiomyopathic hamsters. The increase in CSH diaphragm compliance was observed despite an increase in the surface area of collagen and was not associated with an abnormal distribution of titin or laminin.     

Muscular composition of the gastric groove in the golden hamster

The golden hamster possesses a forestomach and a glandular stomach. The gastric groove connects the cardia to the glandular stomach and is situated on the lesser curvature of the stomach. The constitution of the muscle fibers in the gastric groove was investigated. The gastric groove consisted of two lips and a groove floor. The muscle coat of the lips was composed of a mixture of smooth and striated muscle fibers. The smooth muscle fibers were components of the cardiac muscle loop. The striated muscle fibers were extensions from the esophageal inner circular muscle layer, and invaded about half the length of the lips. The muscle coat of the groove floor consisted of an inner circular muscle layer made up of smooth muscle fibers, and the outer longitudinal muscle layer of the striated muscle fibers extended from the esophageal outer longitudinal muscle layer. The present study revealed that the muscle coat of the gastric groove in the golden hamster was composed of smooth and striated muscle fibers, and that these striated muscle fibers were extensions of the esophageal muscle coat.     

Sex differentiation of t-e circadian system in the golden hamster

The effect of estradiol benzoate (EB) on free-running circadian activity rhythms was studied in gonadectomized hamsters maintained in constant dim illumination. EB shortened the period (tau) of the female, but not of the male circadian activity rhythm. Responsiveness of the circadian system to EB was subject to sexual differentiation. The circadian period of wheel running by female hamsters given a single injection of testosterone propionate on the day of birth did not shorten in response to EB in adulthood. This failure to respond to EB also was observed in normal male hamsters, and was different from the response shown by normal females. Preliminary data suggest that tau of the activity rhythm of males castrated on the day of birth is shortened during EB treatment in adulthood. The differential effects of estradiol on tau are related to anatomic differences between the sexes in neural connections of the substrate for circadian rhythms.     

Melatonin binding sites in the harderian gland of the rat and Syrian hamster

Specific melatonin binding sites in the harderian gland of both rat and Syrian hamster were studied using [125I]melatonin. In both species, binding of [125I]melatonin by harderian gland membranes exhibited properties such as dependence on time, temperature, membrane concentration, saturability, and high specificity. Only one class of high-affinity binding sites was found with a Kd of 0.19 and 6.47 nM for the rat and Syrian hamster, respectively. The binding capacity in the rat harderian gland was 4.00 fmol/mg protein; in the Syrian hamster it was 7.58 fmol/mg protein. In the rat, no sex differences were found in the binding of the tracer to the membranes. However, in the Syrian hamster, binding of [125I]melatonin by the harderian gland was twice higher in the female than in the male. No changes were found in the Kd values (6.47 vs. 6.94 nM), while binding capacity was significantly increased in the female (13.50 fmol/mg protein) when compared to the male hamster (7.58 fmol/mg protein). Binding of [125I]melatonin by the harderian gland of male hamsters was modified by castration but not by melatonin treatment. Castration induced an increase of binding up to the level of females. However, chronic melatonin administration did not alter the [125I]melatonin binding in either intact or gonadectomized male hamsters. Binding studies also showed diurnal variations. There was a diurnal rhythm of [125I]melatonin binding by Syrian hamster harderian glands with the peak at the end of the light period and the trough late in the dark period. This rhythm in the binding is observed in both male and female hamsters, although binding in females was always higher than that in males.(ABSTRACT TRUNCATED AT 250 WORDS)     

A novel, synergistic interaction between 17 beta-estradiol and glutathione in the protection of neurons against beta-amyloid 25-35-induced toxicity in vitro

The present studies were undertaken to investigate the possibility of an interaction between 17 beta-estradiol (E2) and glutathione in protecting cells against the presence of beta-amyloid 25-35 (betaAP 25-35). We demonstrate that when evaluated individually, supraphysiological concentrations of either E2 (200 nM) or of reduced glutathione (GSH; 325 microM) can protect SK-N-SH human neuroblastoma cells from betaAP 25-35 (20 microM) toxicity. This dose of betaAP 25-35 was chosen based on the LD50 (28.9 microM) obtained in our earlier work. However, in the presence of 3.25 microM GSH, the neuroprotective EC50 of E2 was shifted from 126 +/- 89 nM to 0.033 +/- 0.031 nM, approximately 4000-fold. Similarly, in primary rat cortical neurons, the addition of GSH (3.25 microM) increased the potency of E2 against betaAP 25-35 (10 microM) toxicity, as evidenced by a shift in the EC50 values of E2 from 68 +/- 79 nM in the absence of GSH to 4 +/- 6 nM in its presence. The synergy between E2 and GSH was not antagonized by the addition of the estrogen receptor antagonist, ICI 182,780. Other thiol-containing compounds did not interact synergistically with E2, nor were any synergistic interactions observed between E2 and ascorbic acid or alpha-tocopherol. Based on these data, we propose an estrogen-receptor independent synergistic interaction between glutathione and E2 that dramatically increases the neuroprotective potency of the steroid and may provide insight for the development of new treatment strategies for neurodegenerative diseases.     

Linkage group V in the Syrian hamster: cardiomyopathy and lethal gray

It was shown that the cm and Lg genes, which are relatively closely linked, are not linked with markers in any of the four established linkage groups in the Syrian hamster. Therefore, the linkage between these two genes constitutes a new linkage group, LGV.     

2-Hydroxy-4-glutathion-S-yl-17beta-estradiol and 2-hydroxy-1-glutathion-S-yl-17beta-estradiol produce oxidative stress and renal toxicity in an animal model of 17beta-estradiol-mediated nephrocarcinogenicity

Measuring the vertical displacement of the center of mass (COM) of the body during walking may provide useful information about the energy required to walk. Four methods of varying complexity to estimate the vertical displacement of the COM were compared in 25 able-bodied, female subjects. The first method, the sacral marker method, utilized an external marker on the sacrum as representative of the COM of the body. The second method, the reconstructed pelvis method, which also utilized a marker over the sacrum, theoretically controlled for pelvic tilt motion. The third method, the segmental analysis method, involved measuring motion of the trunk and limb segments. The fourth method, the forceplate method, involved estimating the COM displacement from ground reaction force measurements. A two-tailed paired t-test within an ANOVA showed no statistically significant difference between the sacral marker and the reconstructed pelvis methods (p = 0.839). There was also no statistically significant difference between the sacral marker and the segmental analysis method (p = 0.119) or between the reconstructed pelvis and the segmental analysis method (p = 0.174). It follows that the first method, which is the most simple, can provide essentially the same estimate of the vertical displacement of the COM as the more complicated second and third measures. The forceplate method produced data with a lower range and a different distribution than the other three methods. There was a statistically significant difference between the forceplate method and the other methods (p < 0.01 for each of the three comparisons). The forceplate method provides information that is statistically significantly different from the results of the kinematic methods. The magnitude of the difference is large enough to be physiologically significant and further studies to define the sources of the differences and the relative validity of the two approaches are warranted.     

The significance of circadian organization for longevity in the golden hamster

INTRODUCTION: Altered patellofemoral biomechanics may result in pain, instability and early involutive processes. Magnetic Resonance Imaging (MRI), with its panoramic capabilities, has proved to be an effective technique in the study of knee extensor complex changes. The diagnostic advantages of dynamic studies of patellofemoral kinetics are reported in the recent scientific literature. We investigated the diagnostic potentials of passive studies of the knee extensor complex with sagittal and axial cine MRI. Then, we developed and optimized an innovative study method overcoming the limitations of the other dynamic techniques for the correct assessment of patellofemoral biomechanics. MATERIAL AND METHODS: We studied the knee with a .2 T permanent magnet dedicated to the limbs and acquired the images in different positions of flexion-extension with T1-weighted SE and T2-weighted GE sequences. We examined 21 healthy volunteers and 37 of 38 patients with anterior knee joint pain of suspected patellofemoral origin. All the images needed for dynamic studies were acquired in about 20 minutes. For the scan planes not to be affected by patellar motion in the different degrees of knee extension, it is necessary to acquire single axial images to be edited in cine motion afterwards. Each acquisition is aligned along sagittal reference planes depiciting always the same patellar aspect. RESULTS: Significant correlations were found between clinical and cine MR findings in 25 patients. In particular we depicted some extensor complex impingement conditions missed at conventional MRI, which clarified the role played by patellar dysplastic changes in cartilage microtraumas. Our technique was accurate, quite easy to perform and repeatable. We performed cost-effective dynamic studies which were useful in the evaluation of patients with anterior knee pain in whom conventional MRI had failed to provide enough information. CONCLUSIONS: Our technique differs from other passive or active dynamic studies reported on in the literature because the patellar volume does not change during acquisitions. This permits to decrease morphological changes and to simplify, on cine MR reconstructions, the specific analysis of patellofemoral dynamics during flexion-extension. Fewer morphological changes also mean a more accurate analysis showing the role of patellar dysplasia in cartilage microtraumas. Our dynamic MR protocol is accurate, easy to perform and to repeat; it allows dynamic studies in the patients with poor static MR findings.     

Bioactivation of estrone and its catechol metabolites to quinoid-glutathione conjugates in rat liver microsomes

Although the carcinogenic effects of estrogens have been mainly attributed to hormonal properties, there is interest in estrogens acting as chemical carcinogens by binding to cellular macromolecules. In the present study, we explored factors which influence the rate of P450-catalyzed formation of the o-quinones (3,5-cyclohexadiene-1,2-diones) from 2-hydroxyestrone (2-OHE) and 4-hydroxyestrone (4-OHE) as well as from estrone in rat liver microsomes. The initially formed o-quinones were trapped as their GSH conjugates which were separated and characterized by HPLC with electrospray-MS detection. Two mono-GSH conjugates were observed from the 2-OHE-o-quinone as well as a conjugate where GSH had added twice to the molecule producing a di-GSH conjugate. 4-OHE-o-quinone gave only one mono-GSH adduct as well as a di-GSH adduct. Both 2-OHE and 4-OHE were excellent substrates for P450, generating o-quinone GSH adducts at 94 and 40 times, respectively, the rate of estrone. 2-OHE but not 4-OHE saturated P450 at unusually low concentrations (0.2 nmol of P450/mL) perhaps due to differences in the stability of the o-quinones formed in the active site of the enzyme. Preliminary data suggest that the o-quinones of both 2-OHE and 4-OHE could isomerize to quinone methides (4-alkyl-2,5-cyclohexadien-1-ones, QMs). The o-quinones of the catechol estrogens were incubated at 37 degrees C (pH 7.4) in the absence of GSH. Aliquots were removed at various times and combined with GSH. From the pseudo-first-order rate of disappearance of the o-quinone GSH adducts, the half-lives of the o-quinones were determined. The o-quinone from 2-OHE has a half-life of 42 +/- 3 s at 37 degrees C (pH 7.4), and the o-quinone from 4-OHE has a half-life of 12.2 +/- 0.4 min under identical conditions. The o-quinones of the AB ring analogs of the catechol estrogens (3,4-dihydroxy-5,6,7,8-tetrahydronaphthalene and 1,2-dihydroxy-5,6,7,8-tetrahydronaphthalene) isomerize to QMs, suggesting that a similar reaction pathway could occur with the o-quinones from catechol estrogens. In support of this, oxidation of 4-OHE and quenching with GSH after 70 min produced 9-dehydro-4-hydroxyestrone (3-hydroxy-1,3,5-(10),9(11)-estratetraen-17-one), a product which could result from either the QM hydrolysis product or the QM--glutathione conjugate, both of which could eliminate to give the conjugated alkene of 4-OHE. The implications of the o-quinone/QM pathway to the in vivo effects of catechol estrogens are not known; however, given the direct link between excessive exposure to endogenous estrogens and the enhanced risk of breast cancer, the potential for formation of additional reactive intermediates needs to be explored.     

Innervation and nitric oxide modulation of mesenteric arteries of the golden hamster

Immunohistochemical and pharmacological techniques were used to examine perivascular nerves, endothelium and the effects of inhibition of nitric oxide synthesis on responses in mesenteric arteries/perfused mesenteric arterial beds of the Golden hamster. Frequency-dependent vasoconstrictions to electrical field stimulation and dose-dependent vasoconstrictions to noradrenaline were significantly augmented by NG-nitro-L-arginine methyl ester (10(-5) M), an inhibitor of nitric oxide synthase. In preparations with tone raised with methoxamine (10 microM) dose-dependent relaxations to ATP, but not to acetylcholine, were blocked by NG-nitro-L-arginine methyl ester. In the presence of guanethidine (5 microM) to block sympathetic neurotransmission there was no neurogenic relaxation to electrical field stimulation. Furthermore, the sensory neurotoxin capsaicin (0.05-5 nmol) did not elicit relaxation. Immunohistochemical studies demonstrated dense plexuses of fibres immunoreactive for tyrosine hydroxylase and neuropeptide Y, a plexus of moderate density for calcitionin gene-related peptide and an absence of fibres immunoreactive for substance P and vasoactive intestinal polypeptide. Of particular interest is the finding that whereas sympathetic perivascular nerves and nitric oxide regulate the function of hamster mesenteric arteries, there is no apparent motor function of calcitonin gene-related peptide-containing sensory nerves.     

Effects of corticotropin-releasing factor on circadian locomotor rhythm in the golden hamster

Stress produces a reduction in the amplitude of some circadian rhythms. The neurochemical mechanisms underlying stress-induced changes in circadian rhythms are not known. To investigate a possible role of corticotropin-releasing factor (CRF) in this phenomenon, three related experiments were carried out: activity rhythms of male golden hamsters (10/14 hours light/dark entrained, lights on at 0800 h) were measured 1) following the intracerebroventricular administration of CRF (0.5, 1.0, 2.0, or 4.0 microg) at two different times of day, 2) following social stress (30-min resident-intruder confrontation), 3) and following the administration of the CRF-antagonist alpha-helical CRF9-41 (2.0 microg) prior to a 15-min resident-intruder confrontation. CRF produced a significant, dose-related decrease in circadian rhythm amplitude following administration in the morning hours, but not in the afternoon. CRF also induced transient increases in activity post injection concomitant with an activation of the hypothalamic-pituitary-adrenocortical (HPA) system. Stress similarly reduced the amplitude of activity patterns and stimulated the HPA system. The stress-induced depression of circadian rhythm amplitude was significantly attenuated following alpha-helical CRF9-41. These data suggest a role for CRF in the stress-related modulation of circadian locomotor rhythm amplitude.     

Verapamil regulation of a defective SR release channel in the cardiomyopathic Syrian hamster

The Bio 14.6 Cardiomyopathic Syrian Hamster (CMH) has an autosomal recessive disease characterized by intracellular calcium overload, cardiac and skeletal myopathies and premature death from congestive heart failure. Early treatment of these animals with the calcium antagonist, verapamil (V), prevents the development of the disease. We have previously provided evidence supporting a specific defect in the ryanodine-sensitive SR calcium release channel (SRCRC) in CMH. We now provide physiologic and biochemical evidence that V modulates SRCRC. Papillary muscles prepared from F1B control hamsters (F1B) revealed an enhanced inotropic responsiveness to V and ryanodine (R) with age, not seen with CMH. CMH papillary muscles demonstrated paradoxical positive inotropic effects of V and R not shared with F1B. The positive inotropic effects of V and R were not additive. V enhanced the affinity (decreased KD) of [3H]ryanodine binding to cardiac membranes. Thus, V may prevent the overt manifestations of genetic disease in CMH by modulating a defective ryanodine-sensitive SR release channel.     

Differential spatiotemporal regulation of lactoferrin and progesterone receptor genes in the mouse uterus by primary estrogen, catechol estrogen, and xenoestrogen

Many xenobiotics are considered reproductive toxins because of their ability to interact with the nuclear estrogen receptors (ERalpha and ERbeta). However, there is evidence that these xenobiotics can regulate gene expression in the reproductive targets by mechanisms that do not involve these ERs. To examine this further, we compared the effects of estrogenic (o,p'-DDT [1-(o-chlorophenyl)-1-(p-chlorophenyl)2,2,2-trichloroethane] and Kepone, chlordecone) and nonestrogenic (p,p'-DDD [1,1-dichloro-2,2-bis(p-chlorophenyl)ethane], a metabolite of p,p'-DDT) xenobiotics with those of 17beta-estradiol (E2) and 4-hydroxyestradiol-17beta (4-OH-E2), a catechol metabolite of E2, on uterine expression of lactoferrin (LF) and progesterone receptor (PR). These genes are estrogen responsive in the mouse uterus. Normally, LF is expressed in the uterine epithelium, whereas PR is expressed in both the epithelium and stroma in response to estrogenic stimulation. Ovariectomized mice were injected with xenobiotics (7.5 mg/kg), E2 (10 microg/kg), 4-OH-E2 (10 microg/kg), or the vehicle (oil, 0.1 ml/mouse), and uterine tissues were processed for Northern blot and in situ hybridization. The pure antiestrogen ICI-182780 (ICI; 1 or 20 mg/kg) was used to interfere with estrogenic responses that were associated with the ERs. The results of Northern and in situ hybridization demonstrated increased uterine levels of PR and LF messenger RNAs (mRNAs) by all of these xenobiotics, but quantitatively the responses were much lower than those induced by E2 or 4-OH-E2. The results further showed that the E2-inducible epithelial LF mRNA accumulation was markedly abrogated by pretreatment with ICI (20 mg/kg). In contrast, this treatment retained the epithelial expression of PR mRNA, but down-regulated the stromal expression. In contrast, ICI had negligible effects on LF and PR mRNA responses to 4-OH-E2, indicating that this catechol estrogen exerted its effects primarily via a mechanism(s) other than the ERs. The heightened accumulation of LF mRNA in the epithelium in response to Kepone and o,p'-DDT was also severely compromised by pretreatment with ICI, but this antiestrogen had little effect on responses to p,p'-DDD. Similar to E2, Kepone increased the expression of PR mRNA in both uterine epithelium and stroma. However, pretreatment with ICI decreased stromal cell expression, whereas epithelial cell expression remained unaltered or increased. These responses were not noted in mice treated with o,p'-DDT or p,p'-DDD. Collectively, the results demonstrate that catechol estrogens or xenobiotics can alter uterine expression of estrogen-responsive genes by mechanisms that are not totally mediated by the classical nuclear ERs, and these alterations are cell type specific. We conclude that an interaction of a compound with the nuclear ERalpha and/or ERbeta is not an absolute requirement for producing specific estrogen-like effects in the reproductive target tissues.