Stimulation by Bt2cAMP of epidermal mucous metaplasia in retinol-pretreated chick embryonic cultured skin, and its inhibition by herbimycin A, an inhibitor for protein-tyrosine kinase

Epidermal mucous metaplasia of cultured 13-day-old chick embryonic tarsometatarsal skin can be induced by culture in medium containing retinol (20 microM) for only 8-24 h and then in a chemically defined medium without vitamins or serum for 6 days. In the induction of mucous metaplasia, retinol primarily affects the dermal cells and a signal(s) induced in the dermis by excess retinol alters epidermal differentiation toward secretory epithelium. In this work we found that Bt2cAMP (2 mM) stimulated mucous metaplasia severalfold when added to retinol-pretreated skin but inhibited epidermal mucous metaplasia when added together with retinol. Forskolin (100 microM), an activator of adenylate cyclase, also stimulated mucous metaplasia when added to retinol-pretreated skin. On the other hand, transduction in the epidermal cells of a signal(s) induced in dermal cells by excess retinol was inhibited by herbimycin A (500 ng/ml), an inhibitor of protein-tyrosine kinases, and TPA (0.1 microM), an activator of protein kinase C. Hence these findings indicated that cAMP stimulated signal-induced mucous metaplasia, and that transduction of the signal(s) in the epidermal cells required protein-tyrosine kinase and was inhibited by protein kinase C.

Flurbiprofen does not affect elastase-induced bronchial secretory cell metaplasia in hamsters

The anti-inflammatory drug flurbiprofen speeds the repair of cigarette smoke-induced bronchial secretory cell metaplasia (SCM) in rats. We tested whether flurbiprofen would prevent or mitigate the development of elastase-induced bronchial SCM in hamsters. Twice daily injections of flurbiprofen (4 or 6 mg.kg-1.day-1) were begun immediately after intertracheal instillation of porcine pancreatic elastase (PPE) or its vehicle, saline. At 3 wks, the bronchi of these animals were compared to those of animals receiving PPE or saline. PPE-treated hamsters, with or without flurbiprofen, developed moderate to severe SCM. Control hamsters had normal airways. Flurbiprofen had no effect on the neutrophilic pulmonary infiltrate seen 2 h after PPE instillation. We conclude that the development of elastase-induced SCM in hamsters is not affected by a flurbiprofen regimen begun directly after elastase instillation. The pathogenesis of this lesion may involve factors which are insensitive to flurbiprofen or which trigger the lesion immediately upon exposure to the enzyme.

Reversible pancreatic elastase-induced bronchial secretory cell metaplasia in the rat

Porcine pancreatic elastase (PPE) causes irreversible secretory cell metaplasia (SCM) in the intrapulmonary bronchi of hamsters. To determine whether this lesion can be induced in another rodent species, PPE was transorally instilled into the lungs of anesthetized rats. Saline-treated rats served as controls. Animals were killed 1 week, 3 weeks and 3 months after enzyme treatment and the lungs were inflation-fixed with 4% formalin/1% glutaraldehyde in 0.1 M Na cacodylate buffer at pH 7.4. Transverse sections from 3 intrapulmonary airway levels were embedded in paraffin and in glycol methacrylate. The secretory cell index (SCI) was determined from PAS-stained paraffin sections using a standardized scale of 0 to 4. There were no significant differences between SCI values of PPE-treated rats and saline-treated controls at any time point. Secretory cells in methacrylate sections were subclassified into S1, S2 and S3 cells on the basis of increasing amounts of PAS-positive intracellular granules. At one week, there was no effect of PPE on airway level I secretory cells, but significant increases in numbers of S2 and S3 cells were seen in level II and in S3 cells in level III. At 3 weeks, the number of S1 cells were increased in level I and S2 and S3 cells were increased in level III; level II secretory cells were unaffected. Level III secretory cells had returned to normal by 3 months. There were no significant differences between treatment groups in the total number of secretory cells (S1 + S2 + S3) at any airway level or time point examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Dose-response relationship between O6-methylguanine formation in Clara cells and induction of pulmonary neoplasia in the rat by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone

The relationship between the formation of O6-methylguanine (O6MG) and the induction of lung, liver, and nasal tumors in the Fisher 344 rat by the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) was examined in a dose-response study. Animals were treated for 20 wk (3 times/wk) with concentrations of NNK ranging from 0.03 to 50 mg/kg to induce tumors. Steady-state concentrations of O6MG were quantitated, and cytotoxicity was assessed in target cells and tissues after 4 wk of treatment with NNK. No cytotoxicity was detected in the lung during treatment with NNK. The formation of O6MG was greatest in Clara cells compared with macrophages, type II cells, small cells, and whole lung at all doses examined. The difference in adduct concentration between the Clara cell and other pulmonary cell types was most pronounced with low doses of carcinogen. The O6MG:dose ratio, an index of alkylation efficiency, increased 29-fold as the dose of NNK was decreased from 50 to 1 mg/kg of carcinogen. In contrast, only a small increase in alkylation efficiency was observed in type II cells and whole lung. A significant number of tumors were induced in the lung at doses of 0.1 to 50 mg/kg with incidences ranging from 10% at the lowest dose up to 87% in the group of animals which received 50 mg/kg of NNK. A linear relationship was observed when the concentration of O6MG in Clara cells as a function of dose was plotted against the corresponding tumor incidence. This relationship was not observed using DNA adduct concentrations in type II cells or whole lung. The development of pulmonary tumors appeared to involve the formation of alveolar hyperplasias which progressed to adenomas and finally to carcinomas. The majority of adenomas were solid, whereas carcinomas were mainly papillary. Examination of the ultrastructure of the hyperplasias, adenomas, and carcinomas revealed morphological structures (e.g., lamellar bodies, tubular myelin) which are associated with type II cells. Thus, these data suggest that the majority of neoplasms in the lung begin as type II cell proliferations with progression to adenomas and carcinomas within the areas of hyperplasia. The lack of agreement between biochemical and morphological findings makes it difficult to hypothesize a cell of origin for the pulmonary neoplasms. In contrast to the lung, tumors were induced in the liver and nasal passages only after exposure to high doses of NNK. Moreover, both the formation of DNA adducts and cytotoxicity appear obligatory for the generation of tumors in these tissues.(ABSTRACT TRUNCATED AT 400 WORDS)

Pancreatic hepatocytes in Fischer and Wistar rats induced by repeated injections of cadmium chloride

The effects of multiple sc injections of cadmium chloride (CdCl2) on the pancreas of two rat strains (Wistar [WF/NCr] and Fischer [F344/NCr]) were studied by histological and immunohistochemical examinations. A high incidence of hepatocytic foci occurred within the pancreata of both strains that was associated with this cadmium exposure. Although pancreatic hepatocytes (PH) were found in both strains, Wistar rats were more susceptible to cadmium-induced PH formation while showing more tolerance to cadmium in general. The highest incidence of PH was 93% in Wistar rats and 50% in Fisher rats. Dose-related increases in incidence of PH occurred at levels of 360-513 mumol Cd/kg. Number of PH foci/rat correlated well with PH incidence. By avidin-biotin immunohistochemistry, PH exhibited rat albumen and a gap junction protein (Connexin32) found in hepatocytes. PH were frequently seen along with pancreatic acinar atrophy (fatty replacement) and interstitial fibrosis. Thus, it appears that cadmium must be considered one of the most efficacious agents for production of PH within the rat pancreas. The ability of cadmium to induce this transdifferentiation is also clearly dose and strain related.

Syringosquamous metaplasia. A distinctive eruption in patients receiving chemotherapy

Squamous metaplasia of the upper portion of the sweat ducts has been observed in four patients who received chemotherapy; two patients with acute myelogenous leukemia, one patient with testicular carcinoma, and one patient with anaplastic carcinoma of the lung. This change is different (but perhaps related) from what is described in neutrophilic eccrine hidradenitis in patients with acute myelogenous leukemia and other tumors after chemotherapy. Syringosquamous metaplasia may be confused with well differentiated squamous cell carcinoma histologically.

[Pathologic response of the regenerated retinal pigment epithelium (RPE)--affected by sodium iodate (NaIO3)]

Phagocytosis, proliferation and metaplasia to fibroblast-like cells in the regenerated retinal pigment epithelial cell (RPE) were examined after damage caused by administration of sodium iodate. The solution of sodium iodate (40 mg/kg) was given in a single intravenous injection in rats. Three days after injection, RPE showed marked necrotic damage, but in 2 weeks flat regenerated RPE with short microvilli and no basal infolding were seen on Bruch's membrane. Polystyrene particles were then injected into the subretinal space. The rats were sacrificed 6 hours to 4 days after injection of the particles. The regenerated RPE showed phagocytosis within 6 hours. After 48 hours, they showed multilayer proliferation. After 4 days RPE transformed to spindle-shaped fibroblast-like cells. However proliferation and metaplasia of RPE markedly decreased. The results showed significant decrease in the function of regenerated RPE-cells as a result of their damage.

[Pathologic response of the weak damaged retinal pigment epithelium (RPE)--affected by sodium iodate (NaIO3)]

We examined the cellular responses of the retinal pigment epithelium (RPE) damaged by sodium iodate. RPE was damaged by intravenous administration of sodium iodate, 10mg per kg body weight, in rats. This dose of the agent damaged RPE weakly. Twenty-four hours after the administration of sodium iodate, polystyrene particles were injected into the subretinal space trans-sclerally. Rats were sacrificed at 6 hours to 4 days after injection of particles. Twenty four hours after injection of sodium iodate, RPE were weakly damaged. The cell organelles were swollen and ruptured, but cell structures were not destroyed. Then particles were injected into the subretinal space, RPE did not phagocytize the particles until 24 hours after the injection of particles. After 48 hours, RPE showed proliferation. After 4 days, RPE formed thick multilayers in the subretinal space and transformed to spindle shapes, and RPE underwent metaplasia to fibroblast-like cells. However proliferation of RPE was not marked. RPE cells weakly damaged by sodium iodate showed delay in phagocytosis of the particles and decrease in proliferation and metaplasia to fibroblast-like cells.

Exposure of rats and hamsters to sidestream smoke from cigarettes in a subchronic inhalation study

A 90-day feasibility study was performed in which rats and hamsters were exposed to the sidestream smoke of cigarettes. The only histopathological changes observed were hyperplasia and metaplasia of the epithelium covering the dorsal nasal turbinate bones in rats. These effects were reversible within 90 days.

Reversal by retinoids of keratinization induced by benzo[alpha]pyrene in normal hamster tracheal explants: comparison with the assay involving organ culture of tracheas from vitamin A-deficient hamsters

In a defined culture system for hamster tracheal explants, the activity of 12 different retinoids was evaluated for reversal of keratinization induced by exposure to the carcinogen, benzo[alpha]pyrene (BP-HTOC assay). The effects of retinoids in this system were compared to those in a defined culture system for tracheal explants from vitamin A-deficient hamsters (standard-HTOC assay). In both assays, all-trans-retinoic acid (RA) and 13-cis-RA were the most active retinoids. For RA and 13-cis-RA, the values of ED50 determined in the BP-HTOC bioassay were 4 x 10(-12) and 1 x 10(-11) M, respectively, whereas the corresponding values in the standard HTOC assay were 2 x 10(-11) and 3.3 x 10(-10) M. For all 12 retinoids, the ED50 values from the BP-HTOC were lower than those from the standard-HTOC assay, and there was also a statistically significant correlation between the rank-ordering of ED50 values from the 2 assays. Among 3 N-(retinoyl)amino acids examined in both assays, N-(retinoyl)leucine was the most active, N-(retinoyl)phenylalanine the least active, and N-(retinoyl)alanine intermediate. Among a novel series of bifunctional retinoic acid analogues, the dicarboxyl derivative was the most active. On the basis of these results, the BP-HTOC assay appears to be one of the most sensitive assays for retinoids yet developed. This assay is an appropriate model for evaluating the chemopreventive potential of new retinoids in vitro.

Temporal and spatial factors in diethylstilbestrol-induced squamous metaplasia of the developing human prostate

The effects of exogenous estrogen on the developing human prostate were examined in human fetal prostatic rudiments grown for 1 month as subcapsular renal grafts in athymic male nude mice treated with diethylstilbestrol (DES). Prostatic rudiments grown in untreated (control) hosts exhibited normal ductal morphogenesis, growth, and secretory cytodifferentiation. Squamous metaplasia was observed rarely in controls (2 of 22). Conversely, squamous metaplasia was observed in the prostatic utricle and urethra of all 17 specimens grown in DES-treated hosts. Proximal and distal prostatic ducts exhibited DES-induced squamous metaplasia in 13 and 12 of the specimens, respectively. When present, metaplastic changes were mild in the distal ducts. The distribution and intensity of metaplasia were related to the age of the specimen during the period of DES exposure. In specimens grown in DES-treated hosts to a gestational age equivalent of 16.5 weeks or less, squamous metaplasia was only seen in the prostatic utricle and urethra; however, in specimens grown to a gestational age equivalency of 17 weeks or more, squamous metaplasia was observed in the prostatic ducts as well. The nonuniform distribution of estrogen-induced squamous metaplasia within the developing prostatic ductal system emphasizes a regional and age-dependent susceptibility to exogenous estrogens in proximal ductal areas (near the urethra) as compared with distal ductal regions of the developing human prostate.

Syringomatous hyperplasia and eccrine squamous syringometaplasia associated with benoxaprofen therapy

Two patients are described, each of whom developed multiple eruptive lesions on sun-exposed areas within days after starting benoxaprofen therapy. The lesions were 2- to 5-mm papules suggestive of syringomas, and microscopically showed squamous metaplasia of eccrine ducts and focal necrosis of eccrine keratinocytes as well as prominent eccrine hyperplasia. In both cases, the lesions resolved completely after benoxaprofen therapy was discontinued. A theoretical basis for these findings is discussed.

Reproductive tract lesions in male mice treated neonatally with tamoxifen

Male mice of the NMRI/Tg strain were treated with tamoxifen for the first 3 days after birth. The affected mice were sterile, with multiple reproductive tract lesions. These lesions included testicular hypoplasia, intraabdominal testes, epididymal cysts, and squamous metaplasia of accessory glands.

Cytologic examination of the nasal mucosa in formaldehyde-exposed workers

A cross-sectional study of 80 individuals at three locations was undertaken to evaluate the health effects of long-term exposure to formaldehyde in a phenol-formaldehyde impregnating process and to develop a useful protocol for health surveillance of formaldehyde-exposed workers. Results of physical examinations showed a statistically significant prevalence of mucosal irritation in formaldehyde-exposed workers, particularly those with recent exposure. Cytologic examination of exfoliated nasal cells showed atypical squamous metaplasia, which was found to be a function of age. There was no statistical relationship to formaldehyde exposure.

Prevention and reversal by a non-polar arotinoid (Ro 15-0778) of 3,4-benzpyrene- and cigarette smoke condensate-induced hyperplasia and metaplasia of rodent respiratory epithelia grown in vitro

A non-polar arotinoid, Ro 15-0778, has been investigated for its effect on carcinogen-induced changes in rodent respiratory epithelia in organ culture. In neonatal rat tracheas and fetal mouse lungs grown in vitro, 3,4-benzpyrene and cigarette smoke condensate induce an increased proliferation of epithelial cells associated with a loss of secretory activity and of ciliary function. These changes persist in the absence of carcinogens in explants transferred to control medium. Ro 15-0778 alone has no influence on the normal epithelial growth rate or normal differentiation. However, if combined with either benzpyrene or smoke condensate, the arotinoid antagonizes the carcinogen-induced hyperplasia and metaplasia. During simultaneous treatment, it prevents the increase in mitosis and the loss of secretory activity or ciliary function. In explants pretreated with benzpyrene or cigarette smoke condensate, Ro 15-0778 reverses the high proliferation rate and restores secretory differentiation and ciliary function. The compound is of experimental and clinical interest, since--in contrast to most retinoids--it lacks the signs and symptoms of the classical hypervitaminosis A syndrome. It may be justified to consider it for the treatment of early precancerous changes of the bronchial tree.

Retinoid effects on the epidermis

Since metaplasia and gap junction stimulation are prominent features of retinoid activity in embryonic and neoplastic epidermis, it is ironic that the mechanism(s) of retinoid action in postnatal tissues, where these drugs are employed clinically, appears to be different. Histologic studies in both animals and man with both topical and systemic retinoids demonstrate acanthosis, hypergranulosis, and changes in the thickness and organization of the stratum corneum, due to a boost in cell turnover. On an ultrastructural level, desmosomes are actively shed at the level of the spinous layer, leading to many new attachment points along the cell membranes of the outer epidermis. This change coupled with decreased tonofilaments, enhanced keratinocyte autolysis, and intercellular deposition of glycoconjugates (not mucin by standard histochemistry and lectin binding) lead to loosening and fragility of the stratum corneum. The biochemical basis of retinoid activity (in addition to increased cell turnover) appears to be global enhancement of glycoconjugate synthesis and the generation of less mature keratins. These epidermal effects of retinoids can be exploited therapeutically: (1) to cause loosening of thickened stratum corneum, e.g., in psoriasis or ichthyosis; (2) to enhance penetration of pharmacologic agents, e.g., 5-FU, across hypertrophic actinic keratoses; and finally (3) in neoplastic epidermis, where mucous metaplasia and gap junction proliferation occur, retinoids can normalize differentiation.

Induction of colorectal tumors in rats by sulfated polysaccharides

Some sulfated polysaccharides, such as d-CGN, APS, and DSS, have carcinogenicity to the rat colorectum. These materials first induced colitis, secondly squamous metaplasia, and finally tumors at the colorectum. Initially, colitis was located in the columnar epithelium of the rectum and extended proximally thereafter. Squamous metaplasia persisted in almost all experimental rats and progressed irreversibly. The tumors were adenoma, adenocarcinoma, squamous cell papilloma, and squamous cell carcinoma. Macrophages containing these materials were observed in the lamina propria mucosa and submucosa of the colorectum. There were differences in the molecular weight of the substances and their tumor incidences. However, with regard to their carcinogenicity, these sulfated polysaccharides were inferred to be similar to each other in their target organs and process of tumor development. Consequently, these sulfated polysaccharides may be one entity of carcinogenic sulfates.

Eglin-c, a polypeptide derived from the medicinal leech, prevents human neutrophil elastase-induced emphysema and bronchial secretory cell metaplasia in the hamster

Eglin-c (Eg-c), a polypeptide with a molecular mass of 8,100 daltons, was purified from the medicinal leech Hirudo medicinalis. The Eg-c was tritiated by reductive methylation for in vitro studies. Incubation of 2.1 X 10(-10) moles of human neutrophil elastase (HNE) with 3H-elastin in the presence of 8.2 X 10(-10) moles of 3H-Eg-c inhibited 98.7% of the elastolytic activity of the enzyme. Using Sephadex G 100 chromatography and 1.7 moles of 3H-Eg-c per mole of HNE, a 34,000-dalton complex (3H-Eg-c-HNE) was observed. The stability of the complex formed between 3H-Eg-c and HNE that had been inactivated with succinyl-ala2-pro-val CH2Cl was much less than that of the 3H-Eg-c-HNE complex. In vivo studies were carried out in weight-matched groups of anesthetized golden Syrian hamsters given 100, 300, 500, or 2,000 micrograms of Eg-c in 0.5 ml saline intratracheally 1 h before 300 micrograms HNE was administered intratracheally. Control animals received saline followed by HNE or 2 doses of saline 1 h apart. Eight weeks later, lung statics and dynamics were measured in anesthetized animals, followed by histologic study of lung parenchyma and the mucosa of the large intrapulmonary airways. There were no deaths, and final mean body weights were similar in all groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathology of colposcopic findings in 2635 diethylstilbestrol-exposed young women

An analysis of 6055 colposcopically directed biopsy specimens from 2635 diethylstilbestrol (DES)-exposed women and 445 biopsy specimens from 277 nonexposed women was undertaken to correlate microscopic findings with colposcopic patterns. All examinations were performed using a standardized protocol which required that each participant have colposcopy, cytologic smears, and biopsy of abnormal colposcopic lesions. The findings of colposcopic "columnar epithelium, gland openings, and Nabothian cysts" correlated most often with glandular epithelium in the biopsy specimen. "White epithelium," which includes three related colposcopic patterns, mosaicism, punctation, and white epithelium, was associated most frequently (82-93% of cases) with squamous metaplasia, but occasionally with dysplasia and carcinoma in situ (CIS)(0-6%). The presence of dysplasia or CIS in any individual biopsy specimen occurred most frequently with the observation of higher graded lesions by colposcopy or a prior diagnosis of dysplasia.

Quantitative study of secretory cell metaplasia induced by human neutrophil elastase in the large bronchi of hamsters

To explore the time course and the mechanism of development of bronchial secretory cell metaplasia (SCM) induced by human neutrophil elastase (HNE), anesthetized hamsters were injected intratracheally with 300 micrograms highly purified HNE in 0.5 ml saline solution; saline-injected and untreated animals served as controls. At 3, 8, 16, and 21 days after treatment, animals were killed and their lungs fixed by vascular perfusion. Samples from the hilar region of the left lung, containing the main axial airway and its proximal branches, were embedded in Epon-Araldite, and 1 micron sections were stained with methylene blue. Epithelial cells with a luminal border were categorized into three cell types and expressed as a percent of total cells counted (mean 1900 per animal); cells containing at least three mucin granules were classified as secretory, ciliated cells displayed cilia or basal bodies, and cells with none of these characteristics were classified as indeterminate. Percentages of the three cell types in saline-treated animals, at all time points, were comparable to those in the untreated controls. With HNE treatment the secretory cell percentages were higher at 16 days (mean +/- SEM, 36.4% +/- 3.2%) and at 21 days (35.7% +/- 2.9%) than in the untreated animals (18.2% +/- 1.8%, P less than 0.05). The percentage of the indeterminate cells in the HNE group was decreased at days 8, 16, and 21 (7.2% +/- 1.6%, 5.0% +/- 1.4%, and 8.2% +/- 2.5%, respectively) compared with that in the untreated group (21.7% +/- 2.5%, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Proliferative lesions of the glandular stomach and liver in F344 rats fed diets containing Aroclor 1254

Aroclor 1254 was fed to groups of 24 male and 24 female F344 rats, from 7 weeks of age, at dietary concentrations of 25, 50 and 100 ppm for up to 105 weeks. There was a dose- related depression of body weight gain for both sexes and decrease in survival for male rats. Histologically, an increased incidence of gastric intestinal metaplasia and adenocarcinoma was found in both sexes. Hepatocellular adenomas, carcinomas, and eosinophilic and vacuolated hepatocellular foci were usually found in dosed rats only. The number of these foci per unit area of liver was significantly increased in dosed rats, although eosinophilic foci were only found in rats exposed to Aroclor 1254. Basophilic hepatocellular foci were found in similar numbers per square centimeter of liver in controls and treated rats. This finding suggested that eosinophilic hepatocellular foci and tumors arose de novo rather than from the naturally occurring basophilic foci. The appearance of unique, potentially preneoplastic lesions and tumors in the liver and stomach in dosed rats which do not usually occur spontaneously in control rats would support the hypothesis that Aroclor 1254 induced or initiated these unique lesions de novo rather than promoted the growth of any naturally occurring lesions. Nonneoplastic hepatic lesions included degenerative hepatocellular changes and aggregates of macrophages with crystalline cytoplasmic structures and pigment granules.

[Morphogenetic characteristics of the aggregates formed in epithelial and mesenchymal recombinations of the lungs from intact and urethane-exposed mouse embryos]

A study was made of the morphogenesis of organotypic aggregates obtained by epithelial mesenchymal recombinations from the lungs of embryonic mice, intact and treated with urethane. Normal growth and differentiation of organotypic structures were observed in long-term cultures of aggregates obtained by recombinations of the lung epithelium (E) and mesenchyma (M) from intact (i) embryonic mice (EiMi). Hyperplasia and squamous-cell metaplasia (with or without keratinization) of the epithelium were found in aggregates obtained from E and M of the treated mouse embryos (EtMt) and in aggregates obtained by recombinations of lung E and M from intact and treated embryos (EtMi, EiMt). The data obtained suggest that the alterations in epithelial mesenchymal interactions are of great significance for transplacental lung blastomogenesis and that the mesenchymal lung cells play an important part in mediation of the transplacental carcinogenous effects on epithelial target cells via subsequent epithelial mesenchymal tissue interactions.

Long-term responses of the mouse uterus to neonatal diethylstilbestrol treatment and to later sex hormone exposure

The effects of ovariectomy at 1 month of age and continuous 17 beta-estradiol (E2) and/or progesterone (P) replacement on the uterus of BALB/cCrgl mice neonatally treated with diethylstilbestrol [(DES) CAS: 56-53-1; alpha-alpha'-diethyl-4,4'-stilbenediol] or sesame oil were recorded after 1, 4, 7, and 10 months of treatment. DES-exposed uteri were found to be hypoplastic, less responsive to the growth-promoting effects of E2, and more likely to develop smooth muscle abnormalities after continuous hormonal treatment than similarly treated control uteri. Neonatal DES treatment led to leukocytic infiltration, disruption in the organization of the inner circular smooth muscle layer, and development of a population of epithelial cells believed to respond to later E2 treatment by proliferation and stratification (squamous metaplasia). Qualitative and quantitative responses to continuous P treatment and the development of cystic glandular hyperplasia and adenomyosis were found to be unaltered by neonatal DES administration. The relevance of these results to the problems of uterine abnormalities observed in women exposed to DES in utero is discussed.