17 beta-estradiol attenuates fimbrial lesion-induced decline of ChAT-immunoreactive neurons in the rat medial septum

We investigated the neuroprotective effects of 17 beta-estradiol (E2) on medial septal cholinergic neurons following partial unilateral lesion of the fimbriafornix. Adult female rats were ovariectomized (OVX) and, 5 days later, treated with a single intravenous (iv) injection of an estradiol (E2)-chemical delivery system (E2-CDS) or its vehicle hydroxypropyl-beta-cyclodextrin (HPCD). All rats were subjected to partial unilateral electrolytic fimbrial lesion the following day. At 20 days postlesion, brain slices from treated animals were assessed for choline acetyltransferase (ChAT) by immunohistochemistry. Animals treated with HPCD or E2-CDS showed a 44 or 4% decrease, respectively, in ChAT-positive neurons on the lesioned side compared to the nonlesioned side of the medial septum. In a second study using the same lesioning procedure, adult OVX rats received either a subcutaneous E2 pellet implant (n = 6), or, 5 days postovariectomy, a single iv injection of E2-CDS (n = 8) or HPCD (n = 6). Animals treated with HPCD showed a 55% decrease in ChAT-positive neurons on the lesioned side compared to the nonlesioned side of the medial septum. By contrast, rats treated with E2-CDS or E2 pellet had a 14 or 13% decrease, respectively, in ChAT-positive neurons. Interestingly, E2 treatment substantially decreased ChAT-positive neurons on the nonlesioned side of the medial septum in comparison to control animals. The present study suggests that cholinergic neurons in the medial septum are protected from lesion-induced degeneration by treatments which increase brain E2 levels. Thus, E2 may play a neuroprotective role in the basal forebrain cholinergic system.     

Role of gender and vascular endothelium in rat aorta response to 17 beta-estradiol

Estrogen supplementation in postmenopausal women offers significant cardiovascular protection. The mechanism for this benefit is unclear but may be due to an interaction of estrogen with the blood vessel wall (vascular smooth muscle and endothelium). We examined the response of weight-matched female and male endothelium-intact and -denuded aortae to 17 beta-estradiol, its interaction with noradrenaline, and the effect of N-nitro-L-arginine. Estradiol produced relaxation responses that were significantly greater in female endothelium-intact preparations. This response was sensitive to N-nitro-L-arginine, while the response to 17 beta-estradiol in male endothelum-intact and both female and male endothelum-denuded preparations was resistant. Estradiol also inhibited contractions to noradrenaline, which was more pronounced in the female endothelium-intact aortic rings. These data imply that estradiol interacts preferentially with the female vascular endothelium, but there exists an endothelium-independent process that can also be activated in the male aorta. Further studies are warranted to elucidate these differential mechanisms.     

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

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

Synthesis of 17beta-estradiol by isolated ovarian tissues of the pregnant rat: aromatization in the corpus luteum

Corpora lutea from pregnant rats were incubated to determine their ability to produce 17beta-estradiol and to aromatize testosterone in vitro. Corpora lutea and non-luteal ovarian tissues were removed from rats on days 7, 15, and 22 of pregnancy, and these tissues were immediately frozen or incubated separately in medium 199 at 37 C in an atmosphere of 95% O2-5% CO2 for 4 h. 17Beta-Estradiol in tissue and medium were quantified by a highly specific radioimmunoassay. The estradiol content ivnariably increased in non-luteal tissues during incubation, while it decreased or remained the same in incubated corpora lutea. The synthesis in non-luteal tissues, which was 18 to 400-fold greter. The incubation of corpora lutea (5 to 25 mg of tissue) with testosterone (200 ng) on days 7, 15, and 22 of pregnancy resulted in a mean accumulation of 17beta-estradiol in medium of 2.5 x 103 pg/mg tissue, compared with a mean value of 6 pg/mg for luteal tissue removed from the same ovaries and incubated without testosterone. The incubation of corpora lutea from 15-day pregnant rats with (7alpha-3H)-testosterone resulted in 15% conversion to presumptive (7alpha-3H)17beta-estradiol, which was isolated identically to estradiol isolated for radioimmunoassay. Recrystallization to constant specific activity revealed a high degree of radiochemical purity (75%) of the isolated (3H)estradiol. Rat diaphragm muscle and rabbit corpora lutea did not aromatize testosterone to 17beta-estradiol in amounts detectable by radioirpora lutea in vitro is virtually diol by non-luteal ovarian tissues. However,the corpora lutea show a striking capacity to aromatize testosterone, which might explain the high estradiol content of the rat corpora lutea during pregnancy. The physiological significance of this aromatizing system and of 17beta-estradiol in the corpus luteum is unknown but may be related to the luteotropic action of estradiol in the pregnant rat.     

Acute effect of 17 beta-estradiol and lithium on ovariectomized rat brain biogenic amines metabolism

The effect of 17 beta-estradiol (E2) on the response of dopamine (DA) and serotonin (5-HT) to acute lithium in the brains of ovariectomized rats was investigated. An E2 injection (100 ng/s.c.) to ovariectomized rats did not change striatal DA levels, whereas the levels of its metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), increased 30 min later; concentrations of 5-HT and its metabolite, 5-hydroxyindoleacetic acid (5-HIAA), also remained unchanged. In the frontal cortex, DA, 5-HT, HVA and 5-HIAA levels remained unchanged after the E2 injection, whereas DOPAC levels and DOPAC/DA and HVA/DA ratios increased 30 min later. Injection of LiCl (10 mEq) decreased striatal DA levels, increased DOPAC levels and slightly decreased HVA levels; by contrast, frontal cortex DA and HVA levels increased but DOPAC levels were unchanged. A biphasic response of striatal 5-HT levels occurred, increasing shortly after injection of LiCl, followed by a decrease; 5-HIAA levels, however, increased. In the frontal cortex, injection of rats with LiCl led to a gradual increase in 5-HT levels, whereas 5-HIAA concentrations decreased. In the presence of E2, LiCl effected a greater decrease in striatal DA than injection of LiCl alone, advanced the DOPAC peak by 30 min and increased HVA levels; E2 had less effect on the 5-HT response to LiCl, except the decreases in 5-HT and 5-HIAA at 60 min were greater. Furthermore, in the striatum, the increased DA turnover caused by LiCl, estimated by the DOPAC/DA and HVA/DA ratios, was advanced in rats treated with E2. In the presence of E2, LiCl slightly increased frontal cortex DA, DOPAC and HVA levels compared with treatment with LiCl alone, whereas DOPAC levels decreased in rats treated with LiCl + E2 compared with levels in E2-treated rats. Generally, higher levels of 5-HT and 5-HIAA were measured in the frontal cortices of rats treated with LiCl + Ex compared with rats injected with LiCl. These results indicate that E2 potentiates the acute effect of lithium on striatal and frontal cortex DA and 5-HT levels and metabolism, suggesting a role of the hormonal state on this drug response.     

IL-12 is involved in the induction of experimental autoimmune myasthenia gravis, an antibody-mediated disease

IL-12 has been shown to be involved in the pathogenesis of Th1-mediated autoimmune diseases, but its role in antibody-mediated autoimmune pathologies is still unclear. We investigated the effects of exogenous and endogenous IL-12 in experimental autoimmune myasthenia gravis (EAMG). EAMG is an animal model for myasthenia gravis, a T cell-dependent, autoantibody-mediated disorder of neuromuscular transmission caused by antibodies to the muscle nicotinic acetylcholine receptor (AChR). Administration of IL-12 with Torpedo AChR (ToAChR) to C57BL/6 (B6) mice resulted in increased ToAChR-specific IFN-gamma production and increased anti-ToAChR IgG2a serum antibodies compared with B6 mice primed with ToAChR alone. These changes were associated with earlier and greater neurophysiological evidence of EAMG in the IL-12-treated mice, and reduced numbers of AChR. By contrast, when IL-12-deficient mice were immunized with ToAChR, ToAChR-specific Th1 cells and anti-ToAChR IgG2a serum antibodies were reduced compared to ToAChR-primed normal B6 mice, and the IL-12-deficient mice showed almost no neurophysiological evidence of EAMG and less reduction in AChR. These results indicate an important role of IL-12 in the induction of an antibody-mediated autoimmune disease, suggest that Th1-dependent complement-fixing IgG2a anti-AChR antibodies are involved in the pathogenesis of EAMG, and help to account for the lack of correlation between anti-AChR levels and clinical disease seen in many earlier studies.     

The clinical platform for the 17beta-estradiol vaginal releasing ring

All women, regardless of race, culture, or socioeconomic background, experience urogenital atrophy as a result of hypoestrogenism from the menopause. As women go through the aging cycle, their vaginal and urethral epithelium become progressively deprived of estrogen and the tissue loses epithelial thickness, rugation, moisture, vasculature, and elasticity. The pH increases to above 5, infections in the urinary tract and vagina become more prevalent and cytologic study reflects loss of estrogen by a decrease in superficial cells and an increase in basal and parabasal cells. Replacement of estrogen to reverse these changes is the standard of care, with recent attention focused on the local delivery of estrogen by the vaginal route. The first vaginal ring delivery system of estrogen to the urogenital tract recently has been introduced, with the data confirming efficacy and safety of this delivery method for the treatment of urogenital atrophy. In addition, data on the 17beta-estradiol-releasing ring also support excellent patient acceptance of this local vaginal delivery system of estrogen therapy.     

Experimental autoimmune dacryoadenitis. I. Lacrimal gland disease in the rat

Experimental autoimmune dacryoadenitis was produced in Lewis rats by immunization with a single intradermal administration of a 3M KCl extract of exorbital lacrimal gland in CFA, when enhanced by simultaneous i.v. injection of killed Bordetella pertussis. No significant lacrimal lesions were observed in control animals immunized with the extracts of Harderian or salivary glands. Gel filtration of the 3M KCl extract on Sephacryl S-300 column yielded three protein fractions. Only fraction III (MW = 10-55K) induced marked dacryoadenitis following a single injection of 2.0 mg protein in CFA plus pertussis. The infiltrates in the exorbital lacrimal lesions were first apparent around the ducts and associated vasculature. From this area, the infiltrates appeared to spread to the acini drained by these ducts, ultimately involving as much as 30-50% of the gland. The affected glands most commonly showed a diffuse nongranulomatous infiltrate of small lymphocytes, macrophages, and plasma cells; this was focal in nature, involving acinar atrophy and breakdown, and replaced the normal architecture in extreme cases. The Harderian and salivary glands were uninvolved in these animals, suggesting a restricted specificity of this response. Lewis rats immunized with exorbital lacrimal gland fractions I or II in CFA plus pertussis showed only minimal lesions, similar to controls receiving CFA and pertussis without antigen. These findings suggest that an autoantigen exists in the lacrimal gland of the rat that is capable of inducing a specific lymphoproliferative dacryoadenitis.     

Oxidative stress-related parameters in prostate of rats with experimental autoimmune prostatitis

A decline in expiratory flow rates in divers has recently been attributed to chronic exposure to hyberbaric air. Airway hyperresponsiveness (AHR) to stimuli due to a hyperbaric environment may play a certain role in this context. The aim of this study was to determine the prevalence of AHR in compressed air divers and to assess the value of bronchial challenges for prediction of fitness to dive. A cross-sectional sample of 59 healthy male volunteers--28 divers and 31 diving candidates (controls)--who had been found fit to dive in a diving medical examination underwent additional allergy screening (skin prick and serum IgE) and a histamine bronchial challenge. Pre- and postchallenge body plethysmography was completed to assess AHR. AHR to histamine was significantly increased among divers and positively related to diving experience whereas divers and controls did not differ significantly with respect to age, anthropometric data, current smoking habits, skin prick reaction, and elevated serum IgE. Our results indicate an increased prevalence of AHR to nonspecific inhalation stimuli in experienced divers. Bronchial challenge tests may be helpful to detect asthmatics in the medical assessment of fitness to dive and for follow-up examinations during a diver's career.     

Prevention of fatty streak formation of 17beta-estradiol is not mediated by the production of nitric oxide in apolipoprotein E-deficient mice

BACKGROUND: Estrogens have atheroprotective properties, the mechanisms of which remain obscure. Estrogens have recently been reported to increase endothelial NO synthase expression in castrated animals and to prevent the degradation of NO by decreasing superoxide anion production in cultured endothelial cells. In both cases, increased NO bioavailability would promote vasodilation, inhibit proliferation of the adjacent vascular smooth muscle, reduce platelet aggregation, and inhibit monocyte adhesion to the endothelium and the inflammatory reaction induced by cytokines, all key contributors in the development of atherosclerosis. METHODS AND RESULTS: In the present work, the respective roles of 17beta-estradiol and NO in the development of the atherosclerotic process were investigated in castrated apolipoprotein E-deficient (apo E KO) mice, which spontaneously develop fatty streak lesions within 3 months. N(omega)-Nitro-L-arginine methyl ester (L-NAME), an NO synthase inhibitor, 50 mg x kg(-1) x d(-1), increased arterial blood pressure and decreased cerebellum cGMP content, demonstrating the blockade of NO production, but did not influence the atherogenic process in castrated apo E KO mice. CONCLUSIONS: 17Beta-estradiol decreased the size of the aortic lesions approximately threefold, and the magnitude of this vasculoprotective effect was not altered by L-NAME. Moreover, L-NAME increased circulating malonyldialdehyde (MDA)-modified LDL, which was not altered by 17beta-estradiol, leading to a complete dissociation between circulating MDA-modified LDL and parietal lesions.     

Approaches to the replacement of ethinylestradiol by natural 17beta-estradiol in combined oral contraceptives

The strong hepatic estrogenic actions of ethinylestradiol (EE) are very likely to be the cause of the cardiovascular morbidity related to the use of combined oral contraceptives (COCs). This survey presents results of EE replacement in COCs with natural 17beta-estradiol (E2) in the following stages: reduction of EE to daily doses of 0.01 mg and concomitant replacement with E2 (as valerate, EV), complete replacement of EE with E2 using a novel multiphasic combination containing EV and the progestin dienogest (DNG), and the use of natural E2 to develop estrogen sulfamates (J 995) showing sufficient dissociation of uterine from liver estrogenicity. Recent data from preclinical and clinical studies show that these approaches seem to be promising.     

The direct action of 17 beta-estradiol in isolated omental artery from nonpregnant and pregnant women is related to calcium antagonism

OBJECTIVE: Our purpose was to study the mechanism by which 17 beta-estradiol modulates contractile activity in isolated rings of omental artery from nonpregnant and pregnant patients. STUDY DESIGN: Rings of omental artery with intact endothelium from nonpregnant and pregnant women were mounted in organ chambers for isometric tension recording. The concentration-relaxation relationship to 17 beta-estradiol (10(-7) mol/L to 3 x 10(-5) mol/L) was studied in rings contracted with 60 mmol/L potassium chloride (in both the absence and the presence of tamoxifen, 10(-6) mol/L). The effect of 17 beta-estradiol (10(-5) mol/L) on the contraction induced by 60 mmol/L potassium chloride and on the concentration-contraction relationships to both norepinephrine (10(-9) mol/L to 10(-5) mol/L) and calcium ion (0.05 mmol/L to 2.5 mmol/L in calcium-free depolarizing solution) were studied in the presence and absence of tamoxifen (10(-6) mol/L). The maximal contraction, negative logarithm of the concentration producing 50% relaxation or 50% contraction to the reference 60 mmol/L potassium chloride contraction, and the area under the curve were calculated. Data analysis was by one-way analysis of variance, Newman-Keuls test, and two-sample tests as appropriate. Probability values less than 0.05 in a two-tailed test were considered statistically significant. RESULTS: 17 beta-Estradiol relaxed omental arteries contracted with 60 mmol/L potassium chloride, and this effect was potentiated by tamoxifen in both groups. Incubation of the omental arteries with 17 beta-estradiol inhibited contractions induced by 60 mmol/L potassium chloride in rings from both groups of patients, and tamoxifen did not antagonize this effect in either group. Rings of omental artery from the nonpregnant patients (expressed as percentage of the reference potassium chloride contraction) showed greater contraction than rings from the pregnant women when exposed to norepinephrine, a statistically significant difference. 17 beta-Estradiol decreased the norepinephrine-induced contraction in omental arteries from nonpregnant but not pregnant women in a statistically significant way. Tamoxifen did not influence the effect of norepinephrine for either group. 17 beta-Estradiol inhibited calcium ion-induced contraction similarly in rings of omental artery from both nonpregnant and pregnant patients. Tamoxifen potentiated estradiol-induced inhibition in arteries from pregnant patients. CONCLUSIONS: 17 beta-Estradiol inhibits norepinephrine-induced contractions in omental arteries from nonpregnant but no pregnant patients. The inhibition of the ter sion developed after exposure to potassium chloride, norepinephrine, and calcium ion is caused by a calcium channel blocking action.     

Superantigens in autoimmune disease

The recent identification of superantigens (of retroviral origin in mice and bacterial origin in humans) has given rise to several hypotheses linking superantigens to autoimmune responses. The most compelling argument in support of such a link is restricted V beta gene usage by lymphocytes in rheumatoid joint fluid and Sj?gren's syndrome salivary tissue. However, a substantial body of evidence from mouse models militates against a link between the presence of self-superantigen-reactive T-cells and the development of autoimmune disease. Nevertheless, superantigens are powerful instruments for investigating tolerance.     

The fate of 17 beta-estradiol in the plasma of premenopausal and postmenopausal patients with cancer

The patterns of radioactive estrogen metabolities in the plasma of patients with a variety of malignancies were determined after the injection of physiological amounts of 17 beta-estradiol-6,7-3H or of estrone-6,7-3H. The metabolites were separated and isolated from the plasma by the following procedures: a) alumina chromatography, b) modified Brown procedure, and c) gas liquid chromatography. This study showed that the conjugated state of the estrogens varied with the subjects's age. There was a dramatic decrease in the relative quantity of the plasma free estrogens which are converted to sulfates as the age of the patient increased. This change was noted just prior to menopause, suggesting that there are alterations in the conjugation of plasma estrogens which are detectable before clinical menopause.     

Simultaneous presentation of autoimmune thyroiditis and celiac disease in an adult

Celiac disease may be associated with other underlying autoimmune diseases. Among these, thyroid disease has been described in around 10% of the cases with hypothyroidism being the most frequently reported. Clinical suspicion of thyroid involvement in patients with celiac disease is difficult since the symptomatology is scarce or is masked by the picture of malabsorption. Nonetheless, its detection is important since it is not solved by gluten free diet and its correction requires specific treatment. Thyroid function studies, in addition to determination of antithyroglobulin and antimicrosomal antibodies, should be considered in celiac patients refractory to conventional dietetic treatment. We herein present the case of a 65-year-old woman who consulted for a malabsorption syndrome in whom celiac disease of the adult was simultaneously presented with hyperthyroidism secondary to autoimmune thyroiditis.     

Protective action of 17beta-estradiol in cardiac cells: implications for hyperkalemic cardioplegia

BACKGROUND: Hyperkalemic cardioplegic solutions effectively arrest the heart, but may also induce intracellular Ca2+ loading and cellular hypercontracture, which could contribute to ventricular dysfunction associated with global surgical ischemia. Recently, it has been proposed that 17beta-estradiol may possess protective properties in the ischemic myocardium. The purpose of the present study was to examine the action of 17beta-estradiol on cardiac cells exposed to hyperkalemic stress. METHODS: Single ventricular cardiomyocytes, a preparation devoid of vascular and neuronal elements, were isolated from guinea pig hearts, loaded with a Ca2+-sensitive fluorescent probe, and imaged by digital epifluorescent microscopy. The emitted fluorescence of the probe, a measure of intracellular Ca2+ concentration, and cell length were simultaneously recorded during hyperkalemic challenge, in the absence or presence of 17beta-estradiol. RESULTS: In control cardiomyocytes, the cytosolic concentration of Ca2+ was 138+/-11 nmol/L and cell length 93+/-11 microm. Exposure to high K+ (+16 mmol/L KCl) significantly increased cytosolic Ca2+ to 2,191+/-87 nmol/L (p < 0.001), and produced cell shortening (length at 39+/-5 microm; p < 0.001). 17beta-Estradiol (10 micromol/L) acutely prevented high K+ to induce either intracellular Ca2+ loading (144+/-13 nmol/L, p < 0.001) or hypercontracture (91+/-10 microm, p < 0.001). Tamoxifen (10 micromol/L), an antiestrogen, abolished the protective effect of 17beta-estradiol. CONCLUSIONS: We conclude that 17beta-estradiol prevents hyperkalemia-induced Ca2+ loading and hypercontracture through a direct and tamoxifen-sensitive action in cardiomyocytes. This study raises the possibility that 17beta-estradiol should be considered as a cardioprotective adjunct toward a safer hyperkalemic cardioplegia.     

Apoptosis in brain-specific autoimmune disease

Recent neuropathological studies of experimental autoimmune encephalomyelitis have focused attention on the high number of cells in the lesions that show typical morphological features of apoptosis. Surprisingly, it has turned out that the vast majority of apoptotic cells are T lymphocytes and that they actually represent the antigen-specific T-cell population responsible for the induction of the disease. Taken together, these data suggest that clearance of autoimmune inflammation in the nervous system is accomplished by the destruction of the antigen-specific T-cell population within the lesions. This may explain the low level of central nervous system specific T-cell memory formation, as well as previously unexplained phenomena of 'epitope spreading', in autoimmune inflammation of the nervous system.     

Effect of 17beta-estradiol on somatostatin receptor expression and inhibitory effects on growth hormone and prolactin release in rat pituitary cell cultures

Predictions of the minimal size an organism must have to swim along stimulus gradients were used to compare the relative advantages of sensory systems employing spatial (simultaneous) and temporal (sequential) gradient detection mechanisms for small free-swimming bacteria, leading to the following conclusions: 1) there are environmental conditions where spatial detection mechanisms can function for smaller organisms than can temporal mechanisms, 2) temporal mechanisms are superior (have a smaller size limit) for the difficult conditions of low concentration and shallow gradients, but 3) observed bacterial chemotaxis occurs mostly under conditions where spatial mechanisms have a smaller size limit, and 4) relevant conditions in the natural environment favor temporal mechanisms in some cases and spatial mechanisms in others. Thus, sensory ecology considerations do not preclude free-swimming bacteria from employing spatial detection mechanisms, as has been thought, and microbiologists should be on the lookout for them. If spatial mechanisms do not occur, the explanation should be sought elsewhere.     

Proteins in the heat shock-70 family specifically bind 25-hydroxyvitamin D3 and 17beta-estradiol

Most New World primates evolved to express a form of compensated resistance to steroid hormones from the gonads and adrenal glands as well as to the hydroxylated vitamin D3 prohormone, 25-hydroxyvitamin D3 (25OHD3), and the vitamin D hormone 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] originating from the liver and kidney, respectively. We recently demonstrated that this form of resistance is associated with the overexpression of a novel member of the 70-kDa heat shock protein (hsp-70) molecular chaperone family, which we have termed the intracellular vitamin D binding protein (IDBP). In the current report we more closely examine the ligand-binding capability of purified IDBP and two other mammalian hsp-70 family members, heat-inducible (hsp-70) and constitutively expressed (hsc-70) hsp-70 proteins. Purified IDBP, hsp-70, and hsc-70 all bound 25OHD3 with relatively high affinity; the mean Kd for 25OHD3 ranged from 0.5-2.2 nmol/L (rank order: IDBP > or = hsp-70 > or = hsc-70). By Scatchard analysis, high affinity, specific binding of 1,25-(OH)2D3 was not reproducibly observed for any of the three members of the hsp-70 family. Unlike purified IDBP, hsc-70 and hsp-70 were also competent binders of the gonadal steroid 17beta-estradiol (mean Kd for 25OHD3, 2.5 and 6.6 nmol/L by hsc-70 and hsp-70, respectively), but not of two other gonadal hormones, progesterone and testosterone. These data suggest that IDBP is relatively specific for 25OHD3 and that additional hsp-70-like binding proteins are present in unpurified New World primate cell extracts that are specific for 1-hydroxylated vitamin D metabolites as well as other gonadal steroid hormones.