Chronic 17beta-estradiol treatment improves skeletal muscle insulin signaling pathway components in insulin resistance associated with aging.

Insulin resistance is a common feature of aging in both humans and rats. In the case of females, it seems to be related to loss of gonadal function, due mainly due to a decrease in plasma estrogen levels. Several causes have been postulated for this insulin resistance, among them changes in several steps of the insulin pathway. In view of these findings, the purpose of the present study was to examine the role of chronic 17beta-estradiol treatment on insulin sensitivity during the aging process, and its effects on levels of the insulin-sensitive glucose transporter Glut4 (both total and plasma membrane localized), the interaction between p85alpha subunit of PI3-k and IRS-1, Tyr- and Ser-612 phosphorylation of IRS-1 levels, and Ser-473 phosphorylation of Akt. The present findings indicate that 17beta-estradiol treatment is able to minimize the deleterious effect of aging on insulin sensitivity, at least at the level of plasma membrane localized Glut4. Nevertheless further research is needed to determine this conclusively.

Increase in placental apolipoprotein D as an adaptation to human gestational diabetes.

The expression of apolipoprotein D (apo D), a lipocalin involved in defense mechanisms against oxidative stress, in placental tissue samples of pregnancies with gestational diabetes mellitus (GDM) was compared to non-diabetic controls. We have investigated the relationship of apo D with 4-HNE, a major propagation product of lipid peroxidation, in stressed tissues. We included 20 pregnant women with GDM and 30 women with normal ongoing pregnancies as the control group. Placentas were collected and frozen for Western blot or included in paraffin for immunohistochemistry. The intensity of immunostaining was higher for apo D and 4-HNE in GDM samples; however, the differences in expression between the groups was more intense for apo D. Positive signals for both antibodies was detected in the villous trophoblast and adventitia tunica around the large blood vessels for all groups. Specific immunostaining for apo D was noted in some mesenchymal and macrophagic-like cells and this signal increased in diabetic placentas. Densitometry analysis of Western blots showed no significant difference for 4-HNE, but was significantly more intense for apo D in diabetic women. The contradictory results for 4-HNE could be due to changes which are too small and are masked in tissue homogenates. The results for apo D showed a strong relationship with GDM in the placenta that may reflect its suggested function in defense mechanisms against oxidative stress.

Aging in the vestibular nuclear complex of the male golden hamster (Mesocricetus auratus): anatomic and morphometric study.

To study the effects of senescence on the vestibular nuclear complex twenty brainstems from male golden hamsters between 3 and 27 months-old were used and the possible variations in the number of neurons, neuronal morphology and nuclear volume were studied. The neuron profiles were drawn with a camera lucida and Abercrombie's method was used to estimate the total number of neurons. The test of Kolmogorov-Smirnov with the correction of Lilliefors was used to evaluate the fit of our data to a normal distribution and a regression analysis was done to decide if the variation of our data with age was statistically significant. The results of the present study are relevant only for male animals and the effect of senescence could be different in female vestibular nuclear complex. Aging affects the volume of the superior and lateral vestibular nuclei, as well as the nuclear neuronal diameter of the medial vestibular nucleus, but no significant neuronal loss has been appreciated in vestibular nuclear complex related with age. During the aging process we have observed that the distribution of neurons within the vestibular nuclei of the golden hamster does not show important changes and most of their morphometric parameters do not vary significantly.

Apolipoprotein D expression in substantia nigra of Parkinson disease.

Apolipoprotein D (apo D), a lipocalin transporter of small hydrophobic molecules could play an important role in several neurodegenerative diseases. However, its role in those diseases remains unclear. Increments of apo D have been reported in relation with injury and degeneration in the nervous system. Recently increases of apo D level have been reported in schizophrenia, a neuropathologic disease where the oxidative stress and lipid abnormalities may be involved. Apo D could act as a sequestering molecule binding excess of arachidonic acid in cells. In order to determine the relationship between apo D expression and other neurodegenerative pathologies related to oxidative damage, we studied the presence of apo D in the substantia nigra of control and Parkinson disease (PD) subjects. We found dopaminergic neurons were not immunoreactive for apo D, control or PD subjects. However, surrounding glial cells showed immunostaining for apo D and signal increases in PD cases. These findings support the role of apolipoprotein D in neuroprotection and the importance of glia in the amount of this protein in the central nervous system.

[Neuroanatomy of the nuclear vestibular complex in the syrian hamster. Comparison with other mammals]. / Neuroanatomía del complejo vestibular nuclear en el hámster sirio. Comparación con otros mamíferos.

The vestibular complex has been studied since the fifties. The general conclusion of research on many mammals is that the vestibular complex has four main vestibular nuclei and some less constantly associated neuronal groups. The general distribution of the four main vestibular nuclei in the hamster does not differ substantially from that of other mammals: humans, many primates, cat, opossom, rabbit, chinchilla, guinea pig, etc. Of the many associated groups that have been described, we clearly identified groups <>, <>, <>, <>, and the interstitial nucleus of the vestibular nucleus of Cajal. However, the latter seems to be less developed than in other mammals. We present results and a map of serial sections of the vestibular area showing the most characteristic anatomic relations with brainstem structures, and the most relevant cytomorphometric results compared with other mammals.

Aging and the human vestibular nuclei: morphometric analysis.

The data concerning the effects of age on the brainstem are scarce and few works are devoted to the human vestibular nuclear complex. The study of the effects of aging in the vestibular nuclei could have clinical interest due to the high prevalence of balance control and gait problems in the elderly. We have used in this work eight human brainstems of different ages sectioned and stained by the formaldehyde-thionin technique. The neuron's profiles were drawn with a camera lucida and Abercrombie's method was used to estimate the total number of neurons. The test of Kolmogorov-Smirnov with the correction of Lilliefors was used to evaluate the fit of our data to a normal distribution and a regression analysis was done to determine if the variation of our data with age was statistically significant. Aging does not affect the volume or length of the vestibular nuclear complex. Our results clearly show that neuronal loss occurs with aging in the descending (DVN), medial (MVN), and lateral (LVN) vestibular nuclei, but not in the superior (SVN). There are changes in the proportions of neurons of different sizes but they are not statistically significant. The neuronal loss could be related with the problems that elderly people have to compensate unilateral vestibular lesions and the alterations of the vestibulospinal reflexes. The preservation of SVN neurons can explain why vestibulo-ocular reflexes are compensated after unilateral vestibular injuries.

Neuroanatomía del complejo vestibular nuclear en el hamster sirio. Comparación con otros mamíferos / Neuroanatomy of the nuclear vestibular complex in the Syrian hamster. Comparison with other mammals

El complejo vestibular ha sido estudiado desde la década de los cincuenta. Las investigaciones llevadas a cabo en numerosos mamíferos han mostrado como conclusión general que el Complejo Vestibular está constituido por cuatro núcleos vestibulares principales y algunos grupos neuronales asociados más o menos constantes. La distribución general de los cuatro núcleos vestibulares principales en el hámster no muestra diferencias sustanciales respecto a otros mamiferos estudiados: hombre, numerosos primates, gato, opossum, conejo, chinchilla, cobaya, etc. De los numerosos grupos asociados descritos nosotros hemos identificado con claridad los grupos «y», «1», «X», «f» y el núcleo intersticial del núcleo vestibular de Cajal. Sin embargo, este último parece estar menos desarrollado que en otros mamiferos. Presentamos los resultados obtenidos incluyendo un mapa a lo largo del área vestibular en cortes transversales seriados, señalando las relaciones anatómicas más características con las estructuras troncoencefálicas, así como los resultados citomorfométricos obtenidos más relevantes, comparándolos con los descritos en otros mamiferos (AU)

The vestibular complex has been studied since the fifties. The general conclusion of research on many mammals is that the vestibular complex has four main vestibular nuclei and some less constantly associated neuronal groups. The general distribution of the four main vestibular nuclei in the hamster does not differ substantially from that of other mammals: humans, many primates, cat, opossom, rabbit, chinchilla, guinea pig, etc. Of the many associated groups that have been described, we clearly identified groups «y», «l», «x», «f», and the interstitial nucleus of the vestibular nucleus of Cajal. However, the latter seems to be less developed than in other mammals. We present results and a map of serial sections of the vestibular area showing the most characteristic anatomic relations with brainstem structures, and the most relevant cytomorphometric results compared with other mammals (AU)

Size and degeneration increase in herring bodies during aging in hamsters.

The hypothalamo-neurohypophysial tract of young, adult and aged male hamsters was studied at lateral and ventral regions of hypothalamus by means of electron microscopy. Neurosecretory swelling axons (Herring bodies) were usually found as classically described containing abundant neurosecretory granules, mitochondria, few microtubules and profiles of smooth endoplasmic reticulum in all groups of age. However, in aged hamsters, starting at 18-month-old subjects, we observed that the size of some neurosecretory axons was highly increased. Autophagic and degenerative features were seen in the larger ones. These data could suggest abnormal axonal storage or axonal transport blocked during aging. The implications in the role of hypothalamus-neurohypophysial system during aging are discussed.

Pattern of apolipoprotein D immunoreactivity in human brain.

Presence of intracytoplasmatic apolipoprotein D (apo D), a lipophilic ligand transporter, was investigated in normal human brains between 20 and 55 years, using an anti-human apolipoprotein D antibody and extravidin-biotin-enhanced immunohistochemistry. Apo D immunoreactivity was found in neuroglial cells of white matter in all sampled brain regions studied but also in pial cells and perivascular cells. Immunoreactive neurons do not present a uniform pattern throughout the gray matter. The pons and the brainstem show a high immunoreactivity for apo D in several nuclei (olivary, arciforme, cuneado, raphe). In the cerebellum the immunoreactivity appears in some neurons of the Purkinje layer. Finally in the cerebral cortex apo D positive neurons were not observed. These results suggest that apo D role may vary depending of cellular synthesis or location.

Neuronal loss in human medial vestibular nucleus.

The data concerning the effects of age on the brainstem are inconsistent, and few works are devoted to the human vestibular nuclear complex. The medial vestibular nucleus (MVN) is the largest nucleus of the vestibular nuclear complex, and it seems to be related mainly to vestibular compensation and vestibulo-ocular reflexes. Eight human brainstems have been used in this work. The specimens were embedded in paraffin, sectioned, and stained by the formaldehyde-thionin technique. Neuron profiles were drawn with a camera lucida at x330. Abercrombie's method was used to estimate the total number of neurons. We used the test of Kolmogorov-Smirnov with the correction of Lilliefors to evaluate the fit of our data to a normal distribution, and a regression analysis was performed to determine if the variation of our data with age was statistically significant. The present study clearly shows that neuronal loss occurs with aging. The total number of neurons decreases with age, from 122,241 +/- 651 cells in a 35-year-old individual to 75,915 +/- 453 cells in an 89-year-old individual. Neuron loss was significant in the caudal and intermediate thirds of the nucleus, whereas the changes in the rostral third were not significant. The nuclear diameter of surviving neurons decreased significantly with age. There is a neuron loss in the MVN that seems to be age-related. It could help explain why elderly people find it hard to compensate for unilateral vestibular deficits. The preservation of neurons in the rostral third could be related to the fact that this area primarily innervates the oculolmotor nuclei; these latter neurons do not decrease in number in other species studied.

Quantitative ultrastructural evidences suggest no age-related changes in biosynthesis and processing within parvocellular cells of the paraventricular nucleus in hamsters.

The parvocellular neurons of the parvocellular division of the paraventricular nucleus (PVPA) were studied in hamsters at six point ages (from 3 to 30 months old). Standard manual morphometric techniques were used to obtain data of parvocellular activity including nuclear and nucleolar size, as well as the percentage of the cell occupied by Golgi apparatus (GA), mitochondria and rough endoplasmic reticulum (RER). Other directly age-related parameters like amounts of nuclear invagination and lipofuscin have also been studied. No significant differences in the measured subcellular components were detected among groups studied, except slight increases in lipofuscin. No age-related changes were found in the synthesizing apparatus, but a significant decrease in the cell area was observed in older groups. This finding could suggest a reduction in absolute terms in the protein synthesis of the parvocellular neurons during aging. Ultrastructural morphometric observations in parvocellular neurons are discussed in relation to synthesizing activity and hormone production during aging.

[The effects of aging on the volume of human vestibular nuclei]. / Efectos del envejecimiento en el volumen de los núcleos vestibulares humanos.

Elderly persons often have balance disorders, with dizziness that sometimes leads to falls. Changes in the peripheral vestibular system with age, with loss of the hair cells and neurons of Scarpa's nucleus, have been studied for years. However, the changes in the vestibular nuclear complex with age have not been examined. We studied paraffin-embedded brainstems from nine persons of different ages in order to analyze possible changes with age. No abnormalities were observed in the volume or length of the vestibular nuclei, except for a decrease in both dimensions in the superior vestibular nucleus (SNV). All the main vestibular nuclei showed an increase in lipofuscin content with age that seemed to be less marked in the SNV. The low lipofuscin concentration in the SNV could be related with the conservation of vestibular reflexes, the center of which seems to be the SVN, in elderly persons.

Growth inhibition of human breast cancer cells by 1,25-dihydroxyvitamin D3 is accompanied by induction of apolipoprotein D expression.

We have analyzed the effect of 1,25-dihydroxyvitamin D3 on the expression of the gene encoding apolipoprotein D (apoD), a protein component of the human plasma lipid transport system that is overproduced by a specific subset of breast carcinomas. Northern blot analysis revealed that 1,25-dihydroxyvitamin D3 strongly up-regulated apoD mRNA levels in T-47D human breast cancer cells in a time- and dose-dependent manner. The potency of this vitamin as an inducer of apoD expression was stronger than the effect observed for such steroid hormones as androgens and progesterone, described previously as hormonal up-regulators of apoD expression in these cells. A time course study demonstrated that the induction of apoD mRNA reached a level of 5-fold over the untreated cells after 48 h of incubation in the presence of 10(-7) M 1,25-dihydroxyvitamin D3. A dose-response analysis showed that a 10(-6) M concentration of this vitamin consistently induced a maximal accumulation of 7-fold over the control cells. Similar up-regulatory effects on the apoD gene expression were obtained by treatment of T-47D cells with 1,25-dihydroxyvitamin D3 analogues, including MC 903, which is relatively devoid of hypercalcemic side effects in clinical applications. Western blot analysis revealed that the inductive effect of 1,25-dihydroxyvitamin D3 was also reflected at the protein level as an increase of immunoreactive protein in the conditioned media of vitamin-treated cells. This increased expression of apoD was accompanied by an inhibition of cell growth and morphological changes in T-47D cells. By contrast, we did not detect any inductive effect of 1,25-dihydroxyvitamin D3 on apoD gene expression in MDA-MB-231 cells, which are refractory to the growth-inhibitory effects of this compound. On the basis of these results, we propose 1,25-dihydroxyvitamin D3 as an important regulator of the expression of the apoD gene in breast carcinomas. We also suggest that apoD may be of interest as a biochemical marker of the action of 1,25-dihydroxyvitamin D3 derivatives in current studies using these compounds as inhibitors of breast cancer cell growth or as chemotherapeutic agents in the prevention of breast cancer.

The magnocellular neurosecretory system of the hamster hypothalamus: an ultrastructural and morphometric study during lifetime.

A quantitative study regarding the age-related changes occurring in the nucleus and the somatic organelles of neurosecretory magnocellular neurons of the hypothalamo neurohypophyseal system (HNS) was carried out in the hamster at six age-points during animal life. The magnocellular cells of both parts of the supraoptic nucleus (SON) and the paraventricular nucleus (PVN) of male Syrian hamsters between 3 and 30 months of age were examined ultrastructurally. Cells of all age groups present the same morphological ultrastructure. Standard manual morphometric techniques are used to calculate the following parameters related directly or indirectly with cellular activity: nuclear area, nucleolar area, nuclear invagination index and volumetric fractions of some intracellular structures (Golgi apparatus, mitochondria, rough endoplasmic reticulum and lipofuscin). With respect to the cell nucleus, the parameters are not modified during aging. No significant differences in the volume density of subcellular components, except lipofuscin, were detected at the age groups studies. However, there is a positive linear trend among all parameters and age except for the rough endoplasmic reticulum. Our results suggest maintenance of the synthetic activity of the magnocellular neurons in the hamster during aging but in no case an increase in their metabolic activity.

Morphometric analysis of the human vestibular nuclei.

BACKGROUND: Cytoarchitectural investigations of the vestibular nuclei have been undertaken in different species of mammals. These data provide a description of the general architecture of the nuclei but limited information about quantitative characteristics of their cell population. We have recently obtained data about the morphometric parameters of the vestibular nuclei neurons in some species. The application of quantitative image analysis techniques to the research of the cellular morphology in the vestibular area of humans might provide basic information to compare with data from animal studies, taking into account the observed correlation between physiological and morphological properties of vestibular neurons. METHODS: The characteristics of the major vestibular nuclei in humans have been studied with light microscopic techniques in serially cut sections. Camera lucida drawings of the vestibular nuclei and their neurons were made and subjected to computerized image analysis. For each vestibular nucleus, information was obtained about topography, morphological characteristics (i.e., location, volume, and length), and the number and morphometric parameters of their neurons (cross-sectional areas, maximum and minimum diameters). Morphometric data about cell parameters were statistically analyzed by comparing the populations within different parts of each nucleus and from different nuclei. RESULTS: Among the vestibular nuclei, the medial, which is the largest, has the greatest number of neurons, and the interstitial, the least. The lateral and interstitial nuclei contain the largest cells, and the descending nucleus has the smallest cells. The superior nucleus contains cells of intermediate size. The size of cells decreases in a rostrocaudal direction in the medial, lateral, and descending nuclei, the opposite trend being observed in the superior nucleus. Within the superior and medial nuclei, there are discrete areas with cells with distinctive characteristics. CONCLUSIONS: These results suggest that, just as most of the anatomical characteristics of the second-order neurons found in animals have been preserved in humans, so the physiological mechanisms observed in the vestibular system of animals should apply to humans.

Rostrocaudal and ventrodorsal change in neuronal cell size in human medial vestibular nucleus.

BACKGROUND: The present paper describes the cytoarchitectonic, morphometric, and three-dimensional characteristics of the human medial vestibular nucleus (MVN). We also studied the regional distribution, in size, of the different neurons and its possible relationship with a functional polarization of the different regions of the nucleus. METHODS: Nine adult human brainstems (30-50 years of age) without neurological problems were used. Specimens were obtained from necropsy and fixed in 4% paraformaldehyde and 5% acetic acid in distilled water. After fixation, blocks were washed, dehydrated, and embedded in paraffin and serial sectioned at 20 microns. Sections were stained with formaldehydethionin, dehydrated, cleared in eucalyptol, and mounted with Eukitt. MVN neurons were drawn with the aid of a camera lucida at 200-micron intervals at 390 x magnification. Serial 50-micron frozen sections were used to determine the volume of the MVN. The three-dimensional reconstruction of MVN was accomplished with a drawing program in a Macinthosh II computer and an AVS on a Stardent workstation computer. RESULTS: In the three-dimensional reconstruction, the human MVN shows a pyramidal form. The base of this pyramid constitutes the rostral limit, and its vertex forms the caudal border of the MVN. The estimated volume is 30.44 +/- 0.85 mm3, with a neuronal population of 127,737 cells and 4,136 neurons/mm3 in density. The average neuronal cross-section changes from one minimum at caudal level (212.46 +/- 2.04 microns 2) to one maximum at rostral level (491.47 +/- 5.08 microns 2). Four cell types, small (< 200 microns 2), medium (200-500 microns 2), large (500-1000 microns 2), and giant (> 1,000 microns 2) cells, were observed. Medium cells constitute 66%, small cells 18%, and large and giant cells 15% and 1% of the neuronal population. CONCLUSIONS: The MVN shows a variation in neuronal size, and it has the highest neuronal density of all the human vestibular nuclei. Large cells predominate in rostral regions of the MVN, with significant differences in the area and diameter of the cells among rostral, central, and caudal regions. Furthermore, the largest cells are grouped in the ventrolateral part of the nucleus, close to its boundaries with the inferior and the lateral vestibular nuclei. The morphological polarization, with respect to the neuronal size of the MVN, can be related to a functional polarization of rostral and caudal regions of this nucleus.

Ultrastructural and quantitative study of atypical age-related bodies in the hamster brain.

Atypical bodies (ABs), related to aging, are described in the central nervous system of normal aged hamsters. Our study used ultrastructural microscopy and quantitative stereology analysis to study these structures in the hypothalamus and brain stem of 3, 6, 12, 18, 24 and 30 month-old hamsters. We found that these complex bodies have an oval or a round profile with a core of fibrillar or tubular structures rounded by a cytoplasmic crown. We frequently observed accumulations of organelles displaying evidence of degeneration. We found that these structures did not appear until 12 months and their frequency increased with age from 12 to 30 months. Their size can range from 3 to 10 microns, although the median size is 6.5 +/- 0.49 microns in diameter. There is a significant correlation between the quantity of these ABs and the animal's age. Their appearance in both hamster and human normal aging can provide an appropriate animal model to yield more information about the normal aging process. This knowledge of the normal aging process in hamsters may also give new insights into which processes in the human brain occur with normal aging and which ones may be exacerbated as in Alzheimer's disease.

Ultrastructural study of a special type of ependymal cell at paraventricular level of the golden hamster third ventricle.

The present paper describes the presence of a special cell located in the ependymal wall at the level of the paraventricular nucleus. At this level, ultrastructural observation of these ependymal cells, unlike most other mammalian species, shows the presence of nucleolus-like bodies in their cytoplasm and occasionally basal processes. These processes appear perpendicular to the ependymal surface and end in contact with the basal membrane of hypothalamic capillaries. Mitochondria, endoplasmic reticulum and numerous filaments are present in the basal processes. Nucleolus-like bodies or nematosomes consist of round or ovoid unbound masses of granular appearing material of variable density located in the apical cytoplasm of the cells. Some of their ultrastructural characteristics are similar to other ependymal specialized cells which are classically termed tanycytes. These findings point out the possibility that those special cells may also be implicated in a ventricle-blood vessel communication.

Hamster supraoptic nucleus: cytoarchitectural, morphometric, and three-dimensional reconstruction.

BACKGROUND: The present paper describes the cytoarchitectonic, morphometric, and three-dimensional characteristics of the golden hamster supraoptic nucleus (SON) in order to provide an anatomical basis for subsequent morphofunctional studies that use this species as an experimental animal. The dimensions (volume and length) and the number of cells of each part of the supraoptic nucleus were obtained, as well as morphometric parameters of their neurons (cross-sectional area and maximum and minimum diameters). A three-dimensional reconstruction of hamster SON has been made in order to know the spatial morphology of this nucleus and to reveal the structural differences between both parts. METHODS: Ten male adult golden hamsters (Mesocricetus auratus) were used. Animals were anaesthetized and transcardially perfused with 4% paraformaldehyde in 0.1 M phosphate buffer at pH 7.2. The hypothalamic area from seven animals was dissected out, dehydrated, and embedded in paraffin. Serial sections of 10 microns were cut in a coronal plane. Sections were stained with thionin, dehydrated, cleared in eucalyptol, and mounted with Eukitt. To prove the neurosecretory nature to the SON, every fourth section was immunostained against neurophysin by using the peroxidase-antiperoxidase method. To study the neuronal morphometric parameters, all magnocellular neurons of the SON were drawn in sections separated 80 microns with the aid of a camera lucida under 500x magnification. Serial 50 microns thick frozen sections of the hypothalamus from three animals were drawn with camera lucida to determine the volume of the two parts of the SON and to make the three-dimensional reconstruction. RESULTS: The SON extends rostrocaudally 1.98 +/- 0.03 mm from the preoptic area to the tuberal hypothalamic area. Two classical parts can be clearly delimited: principal (SONp) and retrochiasmatic (SONr). The neuronal population of the two parts of the SON appears constituted only by magnocellular neurons. The volume of the SONp is 0.039 +/- 0.03 mm3 and contains about 762 +/- 93 magnocellular cells, with a density of 19,151.8 cells/mm3. The volume of the SONr is 0.126 +/- 0.03 mm3 and contains about 1,296 +/- 132 neurons with a density of 10,536.6 cells/mm3. The three-dimensional reconstruction reveals that the SONp appears located in a more cephalic, lateral, and dorsal position than the SONr, and a clear discontinuity between the two parts is observed. CONCLUSIONS: The present study shows that the classically termed SON, in the hamster, clearly consists of two spatially separated neural populations. The SONr is longer than SONp and has the larger volume and higher number of neurons; however, the neurons of the SONr are smaller in cell area than those of the SONp.

Apolipoprotein D gene induction by retinoic acid is concomitant with growth arrest and cell differentiation in human breast cancer cells.

We have examined the regulation by retinoic acid of the gene encoding apolipoprotein D (apoD), a human plasma protein belonging to the superfamily of the lipocalins that is produced by a specific subtype of highly differentiated breast carcinomas. Northern blot analysis revealed that all-trans-retinoic acid (RA) strongly induced the accumulation of apoD mRNA in T-47D and ZR-75-1 estrogen receptor-positive human breast cancer cells in a time- and dose-dependent manner, while no inductive effect was observed in estrogen receptor-negative cell lines, including MDA-MB-231 and MDA-MB-435. The effect of RA on apoD expression by T-47D cells was at least 12-fold more potent than the effect of the steroids dihydrotestosterone and dexamethasone, which had been previously described as hormonal up-regulators of apoD expression in these cells. A time course study demonstrated that the induction of apoD mRNA reached a level of 15-fold over the untreated control cells after 48 h of incubation in the presence of a 10(-7) M concentration of RA. A dose-response analysis showed that as little as 10(-13) M RA produced an accumulation of 5-fold over the control, while incubation of the cells in the presence of 10(-5) M RA induced a maximal accumulation of 24-fold over the control untreated cells. The induction of apoD mRNA was independent of the synthesis of proteins de novo, as demonstrated by the fact that the induction was also detected in the presence of cycloheximide. The incubation of the cells in the presence of RA did not affect significantly the stability of apoD mRNA. By contrast, treatment of the T-47D cells with RA produced an increase of approximately 8-fold in the rate of transcription of the apoD gene. Furthermore, treatment of the T-47D cells with RA induced the synthesis and secretion to the culture medium of apoD. This increased expression of apoD was accompanied by an inhibition of cell proliferation and a progression through a more differentiated phenotype, suggesting that the mechanisms controlling RA-induced growth arrest, cell differentiation, and apoD synthesis may be directly coordinated in human breast cancer cells.