Mapping of estradiol binding sites through receptor micro-autoradiography in the endometrial stroma of early pregnant mice

Estradiol triggers key biological responses in the endometrium, which rely on the presence and levels of its cognate receptors on target cells. Employing the receptor micro-autoradiography (RMAR) technique, we aimed to provide a temporal and spatial map of the functional binding sites for estradiol in the mouse endometrial stroma during early pregnancy. Uterine samples from days 1.5 to 7.5 of pregnancy were collected 1 h after tritiated- (3H-) estradiol administration and prepared for RMAR analysis. Autoradiographic incorporation of 3H-thymidine (after 1-h pulse) was evaluated over the same gestational interval. Combined RMAR with either histochemistry with Dolichus biflorus (DBA) lectin or immunohistochemistry for detection of the desmin further characterized 3H-estradiol binding pattern in uterine Natural Killer (uNK) and decidual cells, respectively. 3H-estradiol binding levels oscillated in the pregnant endometrial stroma between the mesometrial and antimesometrial regions as well as the superficial and deep domains. Although most of the endometrial stromal cells retained the hormone, a sub-population of them, as well as endothelial and uNK cells, were unable to do so. Rises in the levels of 3H-estradiol binding preceded endometrial stromal cell proliferation. 3H-estradiol binding and 3H-thymidine incorporation progressively decreased along the development of the antimesometrial decidua. Endothelial proliferation occurred regardless of 3H-estradiol binding, whereas pericytes proliferation was associated with high levels of hormone binding. Endometrial cell populations autonomously control their levels of 3H-estradiol binding and retention, a process associated with their proliferative competence. Collectively, our results illustrate the intricate regulatory dynamic of nuclear estrogen receptors in the pregnant mouse endometrium.

No evidence of persisting unrepaired nuclear DNA single strand breaks in distinct types of cells in the brain, kidney, and liver of adult mice after continuous eight-week 50 Hz magnetic field exposure with flux density of 0.1 mT or 1.0 mT

BACKGROUND

It has been hypothesized in the literature that exposure to extremely low frequency electromagnetic fields (50 or 60 Hz) may lead to human health effects such as childhood leukemia or brain tumors. In a previous study investigating multiple types of cells from brain and kidney of the mouse (Acta Neuropathologica 2004; 107: 257-264), we found increased unrepaired nuclear DNA single strand breaks (nDNA SSB) only in epithelial cells of the choroid plexus in the brain using autoradiographic methods after a continuous eight-week 50 Hz magnetic field (MF) exposure of adult mice with flux density of 1.5 mT.

METHODS

In the present study we tested the hypothesis that MF exposure with lower flux densities (0.1 mT, i.e., the actual exposure limit for the population in most European countries, and 1.0 mT) shows similar results to those in the previous study. Experiments and data analysis were carried out in a similar way as in our previous study.

RESULTS

Continuous eight-week 50 Hz MF exposure with 0.1 mT or 1.0 mT did not result in increased persisting unrepaired nDNA SSB in distinct types of cells in the brain, kidney, and liver of adult mice. MF exposure with 1.0 mT led to reduced unscheduled DNA synthesis (UDS) in epithelial cells in the choroid plexus of the fourth ventricle in the brain (EC-CP) and epithelial cells of the cortical collecting duct in the kidney, as well as to reduced mtDNA synthesis in neurons of the caudate nucleus in the brain and in EC-CP.

CONCLUSION

No evidence was found for increased persisting unrepaired nDNA SSB in distinct types of cells in the brain, kidney, and liver of adult mice after continuous eight-week 50 Hz magnetic field exposure with flux density of 0.1 mT or 1.0 mT.

Whole-body and microscopic autoradiography to determine tissue distribution of biopharmaceuticals -- target discoveries with receptor micro-autoradiography engendered new concepts and therapies for vitamin D

Information about the distribution of biopharmaceuticals is basic for understanding their actions. Tissue and cellular localization is a key to function. Autoradiography with radiolabeled compounds has provided valuable information with both low resolution whole-body macro-autoradiography and high resolution microscopic autoradiography (micro-autoradiography). Whole-body macro-autoradiography is a uniform and expedient single method approach, providing convenient dose- and time-related overviews with data similar to those obtained with conventional bioassays - and therefore widely used. However, whole-body macro-autoradiography, like common bioassays, has limitations. High specificity-low capacity sites of binding and deposition frequently remain unrecognized. Lack of cellular resolution can cause false negatives and provide misleading results (e.g., false blood-brain barrier). For micro-autoradiography, different methods are advertised in the literature. Most of them are, however, unsuited for drug localization because of inadequate resolution and frequent artifacts. Most drugs interact with their receptors non-covalently by weak electrostatic forces. Therefore, translocation and loss can occur during tissue preparation. This has complicated the use of micro-autoradiography. Receptor micro-autoradiography has overcome these complications and is a method of choice. It has been validated through several diffusible compounds with known localization, extensively applied. It has contributed numerous discoveries, followed by new concepts and therapies. Pictorial evidence in this review indicates that cellular information is essential, a 'sine qua non' for meaningful drug distribution studies. High resolution cellular microscopic information obtained from autoradiography requires tissue dissection and the necessary precautions for preserving pristine in vivo drug deposition. Receptor micro-autoradiography fulfils these requirements. It reveals crucial information at the subcellular level that cannot currently be obtained with any other type of autoradiography or spectrometric imaging.

Drugs in the brain--cellular imaging with receptor microscopic autoradiography

For cell and tissue localization of drugs, receptor microscopic autoradiography is reviewed, including its development history, multiple testing, extensive applications and significant discoveries. This sensitive high-resolution imaging method is based on the use of radiolabeled compounds (esp. tagged with (3)H or (125)I), preservation through freezing of in vivo localization of tissue constituents, cutting thin frozen sections, and close contact with the recording nuclear emulsion. After extensive testing of the utility of this method, the distribution of radiolabeled compounds has been identified and characterized for estradiol, progestagens, adrenal steroids, thyroid hormone, ecdysteroids, vitamin D, retinoic acid, metabolic indicators glucose and 2-deoxyglucose, as well as extracellular space indicators. Target cells and associated tissues have been characterized with special stains, fluorescing compounds, or combined autoradiography-immunocytochemistry with antibodies to dopamine-beta-hydroxylase, GABA, enkephalin, specific receptor proteins, or other cellular products. Blood-brain barrier and brain entries via capillary endothelium, ependyma, or circumventricular recess organs have been visualized for (3)H-dexamethasone, (210)Pb lead, and (3)H-1,25(OH)(2) vitamin D(3). With this histopharmacologic approach, cellular details and tissue integrative overviews can be assessed in the same preparation. As a result, information has been gained that would have been difficult or impossible otherwise. Maps of brain drug distribution have been developed and relevant target circuits have been recognized. Examples include the stria terminalis that links septal-amygdaloid-thalamic-hypothalamic structures and telencephalic limbic system components which extend as the periventricular autonomic-neuroendocrine ABC (Allocortex-Brainstem-Circuitry) system into the mid- and hindbrain. Discoveries with radiolabeled substances challenged existing paradigms, engendering new concepts and providing seminal incentives for further research toward understanding drug actions. Most notable are discoveries made during the 1980s with vitamin D in the brain together with over 50 target tissues that challenged the century-old doctrine of vitamin D's main role as 'the calcitropic hormone', when the new data made it apparent that the main biological function of this multifunctional sunshine hormone rather is maintenance of life and adapting vital functions to the solar environment. In the brain, vitamin D, in close relation to sex and adrenal steroids, participates in the regulation of the secretion of neuro-endocrines, such as, serotonin, dopamine, nerve growth factor, acetyl choline, with importance in prophylaxis and therapy of neuro-psychiatric disorders. Histochemical imaging with high cellular-subcellular resolution is necessary for obtaining detailed information, as this review indicates. New spectrometric methods, like MALDI-MSI, are unlikely to furnish the same information as receptor microautoradiography does, but can provide important correlative molecular information.

Drug localization and targeting with receptor microscopic autoradiography

This review is an argument in favor of better drug target identification. It presents the many merits and feasibilities of drug localization and target identification through the use of a suitable technique: receptor microautoradiography. Studies of drug targets and target bioavailability require methods with high resolution and sensitivity to gain information for understanding mechanisms of action, sound modeling, prediction of effects, and toxicity. For in vivo localization of drugs in tissues and cells, receptor microautoradiography was specifically designed to preserve both tissue structure and deposition of noncovalently bound diffusible compounds and to enable microscopic viewing, quantitative analysis, and characterization of target sites. This method and its applications are explained here. Pictorial and quantitative data are provided together with a discussion of identified targets that document the utility of receptor microautoradiography. For example, when applied to quantitative studies of vitamin D compounds, pharmacokinetic data of blood differed from those of target tissues and even among target tissues. Many of the target tissues discovered and characterized with receptor microautoradiography remained unrecognized with common ADME procedures, radioassay-HPLC, and whole-body autoradiography. For a visual overview of the multiple vitamin D targets, a drug homunculus has been composed. Such a drug or target homunculus may be created for any drug, dose, and time to aid in documenting and fingerprinting. Receptor microautoradiography also is a sensitive method. It can be used for the study of low-dose stimulatory actions of toxic substances to show relationships of receptor binding to dose-dependent reversal of effects, known as hormesis. In addition, a combination of autoradiography and immunocytochemistry with radiolabeled drug and antibodies to receptor or other cellular product permits further target characterization. In its own league, receptor microautoradiography provides unique information. Through greater detail and certainty, it can validate and complement less-sensitive approaches, decrease the failure rates of current ADMET predictions, and serve as a diagnostic tool and guide for biochemical, functional, and clinical follow-up in drug research and development.

N-Nitrosomorpholine induced alterations of unscheduled DNA synthesis, mitochondrial DNA synthesis and cell proliferation in different cell types of liver, kidney, and urogenital organs in the rat

In order to measure rates of unscheduled DNA synthesis (UDS), mitochondrial DNA synthesis, and cell proliferation, i.e. factors relevant in the early phase of carcinogenesis, young rats received by gavage 200 mg/kg N-nitrosomorpholine (NNM) or vehicle (distilled water), and were injected with 3H-thymidine 24 h later. Autoradiographs from liver, kidney, urethra, prostate, seminal vesicle, and ductus deferens were prepared from deparaffinized sections, using a 250-day exposure time. In the liver, UDS was at least doubled in 2n and 4n hepatocytes. Approximately 3% of these hepatocytes exhibited a fourfold increase in UDS. Such strongly labeled cells were only observed in the liver following NNM exposure. With the exception of renal epithelial cells of the proximal tubule, UDS in epithelial cells of bladder, urethra, ductus deferens, seminal vesicle and prostate was decreased in NNM-exposed rats. Mitochondrial DNA synthesis and cell proliferation were significantly increased only in hepatocytes, and were decreased in all other monitored organs in NNM-exposed rats. The strongly increased UDS and more moderately increased mitochondrial DNA synthesis in a subgroup of hepatocytes suggest that possibly some unrepaired damage persists in the DNA of these cells. The latter cells may be the precursors of so-called foci of hepatocellular alteration, which appear later during the process of carcinogenesis. The increased UDS but decreased rate of proliferation in the renal proximal tubule cells might be related to renal carcinogenesis which is observed in NNM-exposed rats after a long latency period.

Vitamin D sites and mechanisms of action: a histochemical perspective. Reflections on the utility of autoradiography and cytopharmacology for drug targeting

Knowledge about sites and mechanisms of action of vitamin D and its analogs has been greatly advanced by histochemical approaches. High resolution and high sensitivity, combined with the integrative potential of relatively intact histochemical tissue preparations, contributed information that is difficult or impossible to obtain otherwise. In in vivo distribution studies with conventional biochemical assays, target cell populations associated with non-target tissues frequently remain unrecognized without the resolution achieved by cellular autoradiography. Autoradiography, alone or combined with immunohistochemistry when applied to in vivo drug targeting and target characterization, has provided information on cellular-subcellular receptor distribution in over 50 tissues. These discoveries, importantly, contribute to a new understanding of the biological role of vitamin D and challenge the concept of "the calcium homeostatic steroid hormone" as being too narrow. While some of the outstanding effects of vitamin D deficiency and toxicity relate to calcium homeostasis, the vast majority of the target tissues appear not to be primarily related to calcium metabolism, but rather to the activation and regulation of exo- and endocrine secretory and somatotrophic processes such as cell differentiation and proliferation. Also, several highly calcium-dependent tissues such as striated and smooth muscles are not genomic targets for vitamin D. The reviewed data on the diverse and extensive presence of target tissues forecast a high therapeutic potential for vitamin D and especially its low-calcemic analogs, far beyond that which is presently utilized. The evidence provided for vitamin D also testifies to the utility and need to include in vivo cytopharmacology in any target evaluation of bioactive compounds to further the understanding of their mechanisms of action, and to identify preferential targets and their differential therapeutic and toxic potentials.

Uptake, distribution and binding of vertebrate and invertebrate steroid hormones and time-dependence of ponasterone A binding in Calliphora vicina. Comparisons among cholesterol, corticosterone, cortisol, dexamethasone, 5 alpha-dihydrotestosterone, 1,25-dihydroxyvitamin D3, ecdysone, estradiol-17 beta, ponasterone A, progesterone, and testosterone

The presence of specific binding sites for radiolabelled vertebrate-type and arthropod-type steroid hormones was investigated in several organs including salivary gland, and central nervous system of third instar Calliphora vicina larvae by thaw-mount autoradiography. Ponasterone A, a 20-hydroxyecdysone agonist and 20-hydroxyecdysone are the only steroids which bind to nuclear high affinity binding sites. These binding sites are DNA associated while nucleoli show no tracer binding. Ecdysone, an endogenous 20-hydroxyecdysone precursor, is taken up by target cells but no significant nuclear binding occurs. 1,25-Dihydroxyvitamin D3 concentrates in cytoplasm only and its uptake is highest compared to all other steroids. Progesterone and testosterone show weak accumulation in the cytoplasm, while for cholesterol, corticosterone, cortisol, dexamethasone, dihydrotestosterone and estradiol-17 beta, no noticeable uptake occurs. For ponasterone A, a clear time dependence of uptake and intracellular distribution is visible, suggesting the existence and involvement of specific ecdysteroid uptake and transport mechanisms. These results suggest the presence of binding sites for various mammalian steroids in insects. Whether vertebrate steroid hormones or metabolites of them play a role in insects or whether the uptake and binding is based on chemical similarities alone without biological significance remains to be further investigated.

Ecdysteroid receptors in the central nervous system of Manduca sexta: their changes in distribution and quantity during larval-pupal development

Ecdysteroids act initially by binding to nuclear and possibly also extranuclear receptors. The presence and expression of these receptors in the insect brain was investigated in the present study as a means of defining these neurons involved in ecdysteroid-regulated processes at different developmental stages. Early in the fifth larval stadium of Manduca sexta, when endogenous ecdysteroid levels are low, receptors for ecdysteroids in cerebral neurons are either absent or present at low levels. Receptors can be reliably detected only on day 0 and are not found again until day 3.5, at the beginning of the commitment peak in the ecdysteroid titer, when they occur in a small stage-specific population of cells. At this time, ecdysteroid receptors are found mainly in nuclei but are also observed at low levels in cytoplasm. By day 4.8, ecdysteroid receptors are exclusively nuclear, and the number of target cells has increased dramatically in several brain regions, including those with known neurosecretory cell groups. This population and organization of ecdysteroid target cells is constant up to day 6, after which time the number of target neurons declines. By day 7.8, only 10% of the number of labelled neurons seen on days 4.8-6.8 remain in peripheral areas. In the pupal brains, ecdysteroid receptors reappear in a new population of neurons. The results indicate changes in the genomic regulation of a varying neuron population by ecdysteroids during fifth stadium development.

Ecdysteroid binding sites localized by autoradiography in the central nervous system of precommitment fifth-stadium Manduca sexta larvae

Brains and subesophageal ganglia from day 3.5 fifth stadium larvae of Manduca sexta were incubated in vitro with 4 nM tritiated ponasterone A, a 20-hydroxyecdysone analog, to determine whether uptake and specific binding of ecdysteroids occur at a cellular level. These tissues, which were taken just prior to the commitment peak in the hemolymph-ecdysteroid titer, showed saturable uptake of 3H-ponasterone A after 40-60 min of incubation. Uptake was blocked by the addition of 400 nM unlabelled ponasterone A, or of 500 nM or 1000 nM 20-hydroxyecdysone. RH 5849, a synthetic 20-hydroxyecdysone agonist with a long half-life, for which ecdysteroid receptors have low affinity, also reduced ponasterone A uptake at a concentration of 10 microM. Autoradiographs of 4 microns sections of brains revealed distinct nuclear concentrations of silver grains over cell populations in the pars intercerebralis, pars lateralis, and ventral tritocerebrum. Nuclear labelling was also found in many small cells around the mushroom bodies and the neuropil, and between the inner and outer larval optic lobes. Nuclear labelling of cells in the subesophageal ganglion was observed in the fronto-medial and lateral regions, in small cells around the neuropil, and caudally in a few large neurons. In addition to cells with nuclear labelling, both brains and ganglia at this development stage contained cells with exclusively cytoplasmic or both nuclear and cytoplasmic labelling. None of these apparent binding sites were observed in the competition experiments, suggesting that the binding is specific.

Dexamethasone and corticosterone receptor sites. Differential topographic distribution in rat hippocampus revealed by high resolution autoradiography

High resolution light microscopic autoradiography was used, together with regional surveys and combined acridine orange staining, to define in rat hippocampus cellular and subcellular sites of concentration and retention of 3H dexamethasone and to compare the topographic pattern of labeling with that of 3H corticosterone. Nuclear uptake of 3H dexamethasone in the hippocampus is demonstrated for the first time in vivo. With 3H dexamethasone, strongest nuclear radioactive labeling was observed in certain glial cells throughout the hippocampus, followed by strong nuclear labeling in most neurons in area CA1 and in the adjacent dorsolateral subiculum and weak nuclear labeling in granule cells of the dentate gyrus. Neurons in areas CA2, CA3, CA4, and in the dorsomedial subiculum and indusium griseum showed little or no nuclear labeling after 3H dexamethasone. With 3H corticosterone, strongest nuclear labeling was observed in neurons in area CA2 and in the dorsomedial subiculum and indusium griseum, followed by area CA1, then CA3 and CA4; the dentate gyrus contained scattered strongly labeled cells among cells with intermediate nuclear labeling. At the subcellular level, evidence for both nuclear and cytoplasmic accumulation of label was found. The results indicate that dexamethasone and corticosterone have both nuclear and cytoplasmic binding sites and that particular patterns of target cell distribution exist, characteristic for each agent. This suggests a differential regulation of cellular functions for the two compounds. Corticosterone nuclear binding appears to be more extensive and encompasses regions with dexamethasone binding. Whether in certain of these common regions corticosterone binds to the same receptor as dexamethasone, which seems possible, or to different receptors, remains to be clarified.

Vitamin D--soltriol the heliogenic steroid hormone: somatotrophic activator and modulator. Discoveries from histochemical studies lead to new concepts

Evidence from autoradiographic studies with 3H 1,25(OH)2 vitamin D3 (soltriol) about its many sites of nuclear binding and multiple actions suggests that the traditional view of "vitamin D and calcium" is too limited and requires modification. A new concept has been developed which proposes that the skin-derived hormone of sunshine, soltriol, is a somatotrophic activator and modulator that affects all vital systems. Regulation of calcium homeostasis is only one of its many actions. Target tissues for soltriol include not only bone, intestine and kidney, but also brain, spinal cord, pituitary, thyroid, endocrine pancreas, adrenal medulla, enteroendocrine cells, thymus, and male and female reproductive organs. Accordingly, actions of soltriol involve effects on autonomic and endocrine regulation with changes in tissue and blood hormone levels, innervation of skeletal muscle, immune and stress response, digestion, blood formation, fertility, pregnancy and lactation, general energy metabolism, mental processes and mood, and others. The skin-mediated transduction of short-wave sunlight induces a purposeful modulation of growth, reproduction and other biological activities in tune with the conditions of the sun cycle and season. Synthesis and actions of vitamin D3-soltriol are dependent not only on the amount of sunlight, but also on the availability of precursor in the skin and access of sunlight, the rate of hydroxylation in liver and kidney, and the modulation of these events by the endocrine status, in particular growth and reproduction. A concept of a five-level control of soltriol synthesis is proposed, in which the hydroxylation steps provide for a sensitive tuning. Relationships between the heliogenic skin-derived hormonal system and the helioprivic pineal-derived hormonal system are recognized and a comprehensive concept of the "endocrinology of sunlight and darkness" is pointed out.

1,25-Dihydroxyvitamin D3 target cells in immature pancreatic islets

Target cells of 1,25-dihydroxyvitamin D3 were identified by autoradiography in islets from rats of different ages. Nuclei of pancreatic islet cells selectively concentrated 1,25-[3H]dihydroxyvitamin D3 but not 25-[3H]hydroxyvitamin D3 or 24,25-[3H]dihydroxyvitamin D3. Developmental studies of pancreatic islets indicated that target cells, as revealed by significant nuclear concentration of 1,25-[3H]dihydroxyvitamin D3, are present in islet cells of fetal rats. The percentage of islet cells that concentrated 1,25-[3H]dihydroxyvitamin D3 increased from 10 to 15% in the fetus to 60% at 1 day of age. Immunocytochemical staining indicated that insulin-containing cells but not glucagon or somatostatin cells concentrated 1,25-[3H]dihydroxyvitamin D3. Peak uptake of 1,25-[3H]dihydroxyvitamin D3 was calculated to be 400 pmol/mg DNA, with no significant difference in nuclear accumulation between islet cells from neonatal and adult rats or between islets in vivo and isolated islets in vitro. The results of these studies indicate that 1,25-[3H]dihydroxyvitamin D3 target cells are present in islets before pancreatic beta-cells are morphologically or functionally mature; islet beta-cells concentrate 1,25-dihydroxyvitamin D3, but not 25-hydroxyvitamin D3 or 24,25-dihydroxyvitamin D3. We conclude that only the 1,25-dihydroxyvitamin D3 metabolite of vitamin D is accumulated by nuclei of developing and mature beta-cells and suggest that 1,25-dihydroxyvitamin D3 plays a role in the maturation of islet beta-cells.

Vitamin D sites of action in the pituitary studied by combined autoradiography-immunohistochemistry

Adult male and female mice under normal diet were injected with 3H 1,25(OH)2 vitamin D3 and sacrificed 3.5 h afterwards. Autoradiograms were prepared according to our thaw-mount technique and stained with antibodies to pituitary hormones. Thyrotropes showed strong and extensive nuclear concentration of radioactivity: about 90% of the immunostained thyrotropes were labeled. Lactotropes, somatotropes and gonadotropes showed no or only weak nuclear radioactivity: a subpopulation of 5%-10% of each of these immunostained cell types displayed nuclear labeling that was weak when compared to thyrotropes. Neural lobe pituicytes also showed weak to intermediate nuclear labeling. The results indicate a presence of nuclear receptors for 1,25(OH)2 vitamin D3 in pituitary cell types and suggest direct but differential genomic effects of 1,25(OH)2 vitamin D3 on pituitary hormone secretion. Evidence further suggests the existence of a vitamin D regulated brain-pituitary-thyroid axis.

1,25 (OH)2 vitamin D3 sites of action in the brain. An autoradiographic study

After injection of 3H 1,25 (OH)2 vitamin D3 to adult rats and mice, under normal or vitamin D deficient diet, the hormone was found to be accumulated in nuclei of neurons in certain brain regions. Nuclear concentration was prevented or diminished, when excess unlabeled 1,25 (OH)2 vitamin D3 was injected before 3H 1,25 (OH)2 vitamin D3, while excess 25 (OH) vitamin D3 did not prevent nuclear labeling. Highest nuclear concentration of 3H 1,25 (OH)2 vitamin D3 is observed in certain neurons in the nucleus interstitialis striae terminalis, involving its septo-preoptic pars dorsolateralis and its anterior hypothalamic-thalamic portion, and in the nucleus centralis of the amygdala, all constituting a system of target neurons linked by a component of the stria terminalis. Nuclear concentration of 3H 1,25 (OH)2 vitamin D3 is also found in neurons in the periventricular nucleus of the preoptic-hypothalamic region, including its extensions, the parvocellular paraventricular and arcuate nucleus, in the ventromedial nucleus, supramammillary nucleus, reticular nucleus of the thalamus, ventral hippocampus, caudate nucleus, pallium, in the midbrain-pontine central gray, dorsal raphe nucleus, parabrachial nuclei, cranial motor nuclei, substantia gelatinosa of the sensory nucleus of the trigeminus, Golgi type II cells of the cerebellum, and others. The extensive distribution of target neurons suggests that 1,25 (OH)2 vitamin D3 regulates the production of several aminergic and peptidergic messengers, and influences the activity of certain endocrine-autonomic, sensory and motor systems.

Autoradiographic studies with 3H 1,25 dihydroxyvitamin D3 in thyroid and associated tissues of the neck region

Rats and mice fed a vitamin D-deficient or vitamin D-complete diet were injected with 3H 1,25 (OH)2 vitamin D3. Autoradiograms prepared from cross sections through the neck region revealed nuclear concentration of radioactivity strongest in parathyroid chief cells, occasionally in thyroid follicular epithelial and interfollicular cells, in the epithelium of tubular remnants of the ultimobranchial body, in epithelium of the esophagus, in chondrocytes of tracheal cartilage, and in myoepithelial cells of tracheal glands. In the thyroid, most of the follicle epithelial cells did not show nuclear concentration of radioactivity which occurred only occasionally and predominantly in follicles located in marginal positions. Thyroglobulin in lumina of thyroid follicles contained varying amounts of radioactivity that correspond to the diameter of the follicles, with relatively high amounts in large follicles and little or no radioactivity in small follicles. Competition with excess of unlabeled 1,25 (OH)2 vitamin D3 abolished nuclear radioactivity, but not the radioactivity in the colloid, while 25 (OH) vitamin D3 did not affect either. When a combination of autoradiography and immunohistochemistry was applied, follicular and parafollicular C-cells positive for calcitonin antibodies, did not show nuclear concentration of radioactivity. Tubular remnants of ultimobranchial bodies, however, showed distinct nuclear labeling, but did not stain, or only weakly stain, with antibodies to calcitonin. When 3H 25 (OH) vitamin D3 was injected, no nuclear concentration of radioactivity was noted in any of the tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Autoradiographic determination of catechol estrogen binding sites in brain, pituitary and uterus

The anatomical pattern of nuclear binding of 2-OH[6,9-3H]estradiol ([3H]2-OHE2) in brain, pituitary and uterus have been studied autoradiographically. Autoradiograms of forebrain, pituitary and uterus show nuclear concentrations of radioactivity in certain cells. This nuclear concentration is abolished when unlabelled 2-OHE2 or E2 was injected prior to the injection of [3H]2-OHE2. In the brain nuclear labelling is observed in the septal-preoptic region, in the anterior hypothalamic area, and in the central hypothalamic area. Some estrogen-sensitive nuclear groups, such as lateral septum and hippocampus, do not show accumulation of radioactivity. In the uterus, luminal and glandular epithelium, stromal cells and muscle cells are labelled. A comparison of the quantitative nuclear uptake of radioactivity and of the different time intervals after the injection of different doses shows similar uptake of nuclear radioactivity. This is comparable to data obtained after [6,7-3H]estradiol ([3H]E2) injection. The results provide clear evidence for nuclear binding of catechol estrogens of the same magnitude as [3H]E2 after in vivo treatment.

The localization of 3H-estradiol in estrogen receptor-positive human mammary carcinoma as visualized by thaw-mount autoradiography

Biochemical assays of human mammary carcinomas for estrogen receptors (ER) are of proven clinical usefulness. The reliability of histochemical or immunocytochemical methods for ER localization are less well established, and less is known about the distribution of estrogen binding proteins in breast cancer. In this report we present results of a study of the uptake and retention of 3H-estradiol after in vitro incubation as visualized by thaw-mount autoradiography in five cases of biochemically estrogen receptor-positive breast cancer. These neoplasms appeared to be composed of a heterogeneous population of labeled and unlabeled tumor cells. The number of nuclear grains varied among putative target cells, and the relative percentage of labeled cells differed from area to area. Non-neoplastic mammary ductal epithelium on occasion revealed significant nuclear labeling, but stromal cells, inflammatory cells, and endothelial cells were generally negative. The possible significance of these findings is discussed.

Brain target sites for 1,25-dihydroxyvitamin D3

Autoradiographic studies with 3H-labeled 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] demonstrate, in certain neurons of rat forebrain, hindbrain, and spinal cord, a nuclear retention and concentration of radioactivity, which can be prevented by treatment with 1,25(OH)2D3, but not with 25-hydroxyvitamin D3. These results indicate the presence of brain receptors in addition to pituitary receptors for 1,25(OH)2D3 and suggest a central modulation of calcium homeostasis and other central effects for this hormone. The existence of a brain-pituitary axis for certain 1,25(OH)2D3-mediated endocrine-autonomic effects is postulated.