Estrone - a partial estradiol antagonist in the normal breast.

Oral hormone replacement therapy (HRT) based on estradiol-17ß (E2) greatly increases circulating estrone (E1) levels. E1 is an estrogen receptor agonist but may also be a partial E2 antagonist. We investigated the effects of circulating E1 on the association between circulating E2 and the increase in mammographic density (∂MD) in 46 healthy post-menopausal women treated with E2 2 mg and norethisterone acetate 1 mg daily. MD and serum E1 and E2 were measured before and after 6 months of treatment. At high E1 levels, ∂MD showed significant positive correlations leading to increase (∂-values) in both E1 and E2. Lowering the upper serum E1 limit strengthened the correlations to ∂E2 while the significant correlations to ∂E1 disappeared. E1 at high concentrations may act as a partial E2 antagonist also in the normal breast in vivo and disturb relationships between circulating E2 and biological estrogen effects. When investigating the relations between circulating steroids and their effects, structurally related compounds, which may act as partial antagonists, have to be considered, at least when they are present in higher concentrations.

Preliminary results using a kit to measure tamoxifen and metabolites concentrations in capillary blood samples from women with breast cancer.

The aim of the study was to compare 3 blood sampling methods, including capillary blood sampling, for determining Tamoxifen (TAM), Z-endoxifen (END), and 4-hydroxytamoxifen (4HT) concentrations. High performance liquid chromatography-mass spectrometry was used to quantify concentrations of TAM, END, and 4HT in plasma, venous blood, and capillary blood samples of 16 participants on TAM therapy for breast cancer. The rhelise kit was used for capillary sampling. Calibration curves using 13C-labeled analogs of TAM, END, and 4HT as internal standards were used for quantifications. A capillary sampling kit was used successfully for all participants. Mean TAM concentrations did not differ significantly in the 3 types of samples. Mean END and 4HT concentrations did differ significantly between capillary and venous blood samples, possibly related to photodegradation in the internal standards prior to use or degradation products with chromatographic retention times similar to the metabolites. TAM, END, and 4HT concentrations were relatively stable when stored for 14 days at 8 °C and 20 °C. Therapeutic drug monitoring of TAM using an innovative kit and capillary blood sampling is feasible. Preliminary data from this study will aid in developing a multicenter, randomized clinical trial of personalized TAM dose monitoring and adjustments, with the goal of enhancing the quality-of-life and outcomes of patients with breast cancer.Clinical Trial Identification: EudraCT No 2017-000641-44.

Fluorene-9-bisphenol is anti-oestrogenic and may cause adverse pregnancy outcomes in mice.

Bisphenol A (BPA) is used in the production of plastic but has oestrogenic activity. Therefore, BPA substitutes, such as fluorene-9-bisphenol (BHPF), have been introduced for the production of so-called 'BPA-free' plastics. Here we show that BHPF is released from commercial 'BPA-free' plastic bottles into drinking water and has anti-oestrogenic effects in mice. We demonstrate that BHPF has anti-oestrogenic activity in vitro and, in an uterotrophic assay in mice, induces low uterine weight, atrophic endometria and causes adverse pregnancy outcomes, even at doses lower than those of BPA for which no observed adverse effect have been reported. Female mice given water containing BHPF released from plastic bottles, have detectable levels of BHPF in serum, low uterine weights and show decreased expressions of oestrogen-responsive genes. We also detect BHPF in the plasma of 7/100 individuals, who regularly drink water from plastic bottles. Our data suggest that BPA substitutes should be tested for anti-oestrogenic activity and call for further study of the toxicological effects of BHPF on human health.

Simultaneous determination of erlotinib and tamoxifen in rat plasma using UPLC-MS/MS: Application to pharmacokinetic interaction studies.

Tamoxifen (TAM) is a non-steroidal estrogen receptor antagonist that enhances erlotinib (ERL)-induced cytotoxicity in the treatment of NSCLC. ERL and TAM are metabolized by CYP3A4 enzymes. In addition, both drugs have the potential of altering the enzymatic activity through either inhibition (ERL) or induction (TAM). Thus it was expected that pharmacokinetics (PK) drug-drug interactions (DDIs) could be encountered following their co-administration. In this respect, a bioanalytical UPLC-MS/MS method has been developed and validated for the simultaneous determination of ERL and TAM in rat plasma samples, using ondansetron (OND) as an internal standard (IS). Plasma samples were prepared using mixed mode cationic solid phase extraction (SPE) STRATA™ -X-C 33µm cartridges with good extraction recovery of both drugs from rat plasma (Er% from -13.92 to -3.32). The drugs were separated on a Waters BEH™ C18 column with an isocratic elution using a mobile phase composed of a mixture of acetonitrile and water, each with 0.15% formic acid, in the ratio of 80: 20, v/v. Quantitation was carried out using the positive ionization mode with multiple reaction monitoring (MRM) at m/z 394.20>278.04 (ERL), m/z 372.25>72.01 (TAM), and m/z 294.18>170.16 (OND). The method was fully validated as per the FDA guidelines over the concentration range of 0.2-50ng/mL with very low lower limit of quantification (LLOQ) of 0.2ng/mL for both ERL and TAM. The intra- and inter-day assay precision (in terms of relative standard deviation, RSD) and accuracy (in terms of percentage relative error, % Er) were evaluated for both drugs and the calculated values evaluated at four different concentration levels were within the acceptable limits (<15%) for concentrations other than LLOQ and 20% for LLOQ. The method was successfully applied to the study of possible PK-DDI following the oral administration of ERL and TAM in a combination, compared to their single administration.

Miniaturized ionic liquid dispersive liquid-liquid microextraction in a coupled-syringe system combined with UV for extraction and determination of danazol in danazol capsule and mice serum.

In this study, for the first time, a coupled 1-mL microsyringe system was utilized to perform a miniaturized ionic liquid dispersive liquid-liquid microextraction (IL-DLLME) method. Danazol was extracted and determined via the developed method followed by micro-volume ultraviolet spectroscopy (UV). The extraction process was carried out by the injection of extraction solvent ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate [C8mimPF6] into sample solution (syringe A), and then rapid shoot the solution into syringe B. After that the shooting was repeated several times at a rate of 1 cycle/s. The extraction procedure was induced by the formation of cloudy solution, which was composed of fine drops of [C8mimPF6] dispersed entirely into sample solution with the help of shooting without any dispersive solvent, ultrasonication or high temperature. Several important parameters affecting the extraction efficiency were studied and optimized. Under the optimized conditions, the limit of detection (LOD) was 0.055 µg/mL (capsule) or 0.054 µg/mL (serum) at a signal-to-noise ratio of 3. The calibration curve was linear over the range of 0.62-25 µg/mL. The proposed method was successfully applied to danazol capsule and the real mice serum samples and good spiked recoveries in the range of 90.5-103.4% were obtained. The obtained results of this work were in good agreement with the results of HPLC.

Tamoxifen disrupts the reproductive process in gilthead seabream males and modulates the effects promoted by 17α-ethynylestradiol.

17α-Ethynylestradiol (EE2), which is used in oral contraceptives and hormone replacement therapy, is a well documented estrogenic endocrine disruptor and an aquatic contaminant. In the present study, adult male specimens of the marine hermaphrodite teleost gilthead (Sparus aurata L.) were fed a diet containing tamoxifen (Tmx), an estrogen receptor ligand used in cancer therapy, alone or combined with EE2, for 25 days and then fed a commercial diet for a further 25 days (recovery period). The effects of short (5days) and long (25 days) treatments on several reproductive and gonad immune parameters and the reversibility of the disruptive effects after the recovery period were examined. Our data showed that Tmx acted as an estrogenic endocrine disruptor as revealed by the increase in the hepatic transcription of the vitellogenin gene in males, the serum levels of 17ß-estradiol and the gonad expression levels of the estrogen receptor α and G protein-coupled estrogen receptor genes, and the recruitment of leukocytes into the gonad, a well known estrogenic-dependent process in gilthead seabream males. On the other hand, Tmx also increased sperm concentration and motility as well as the serum levels of androgens and the expression levels of genes that codify for androgenic enzymes, while decreasing the expression levels of the gene that code for gonadal aromatase. When applied simultaneously, Tmx and EE2 could act in synergy or counteract, each other, depending on the parameter measured. The disruptive effect of EE2 and/or Tmx was not reversible after a 25 day recovery period.

Combined effects of dehydroepiandrosterone and EM-800 on bone mass, serum lipids, and the development of dimethylbenz(A)anthracene-induced mammary carcinoma in the rat.

Although treatment with dehydroepiandrosterone (DHEA) and the antiestrogen EM-800 alone decreased dimethylbenz(A)anthracene (DMBA)-induced mammary tumor incidence from 95% to 57% and 38%, respectively, approximately 9 months after DMBA administration, only two tumors developed in the group of animals that received the combination of DHEA and EM-800, and these two tumors disappeared before the end of the experiment (P < 0.01 vs. DHEA or EM-800 alone). Average tumor number per tumor-bearing animal as well as average tumor area per tumor-bearing animal were further decreased in animals that received the combination therapy compared with the effect of each treatment alone (P < 0.01). DHEA induced 6.9% (P < 0.01), 10.6% (P < 0.05), and 8.2% (P < 0.01) increases in bone mineral density of total skeleton, lumbar spine, and femur, respectively. The addition of EM-800 to DHEA did not affect the enhancing effect of DHEA on bone mass. The combination of the two drugs had important inhibitory effects on the urinary excretion of calcium and phosphorus as well as on the urinary hydroxyproline/creatinine ratio. Serum total alkaline phosphatase was stimulated by DHEA. Treatment with EM-800 decreased both serum triglyceride and cholesterol levels, whereas DHEA had an inhibitory effect on serum triglycerides. Although treatment with EM-800 caused a marked atrophy of the mammary gland, DHEA alone reduced lobular hyperplasia seen in aged intact rats while causing an androgen-specific stimulation of the same structures in animals already receiving the antiestrogen EM-800. The combination of DHEA and EM-800 lowered ovarian weight by 24% (P < 0.01) and decreased serum estradiol concentrations to intact control levels, whereas each compound alone had no effect on ovarian weight and stimulated serum estradiol levels by 45% (P < 0.05) and 46% (P < 0.05), respectively. Treatment with EM-800 caused a marked inhibition of uterine and vaginal weight. The present data show the additive inhibitory effects of DHEA and EM-800 on the development of DMBA-induced mammary carcinoma in the rat, thus suggesting the potential benefits of such a combination for the prevention of breast cancer in women while preserving or even increasing bone mass and maintaining a favorable lipid profile.

Tamoxifen and toremifene concentrations in plasma are greatly decreased by rifampin.

BACKGROUND: Rifampin (INN, rifampicin) is a potent inducer of cytochrome P450 (CYP) enzymes involved in drug metabolism and therefore causes many drug interactions. METHODS: The effects of rifampin on the pharmacokinetics of tamoxifen (study I) and toremifene (study II) were examined in 2 randomized, placebo-controlled crossover studies. Ten (study I) or 9 (study II) healthy male volunteers took either 600 mg rifampin or placebo orally once a day for 5 days. On the sixth day, 80 mg tamoxifen or 120 mg toremifene was administered orally. Blood samples were collected up to 336 hours after drug administration. RESULTS: Rifampin reduced the area under the plasma concentration-time curve (AUC) of tamoxifen by 86% (P < .001), peak plasma concentration (Cmax) by 55% (P < .001), and elimination half-life (t1/2) by 44% (P < .001). The AUC of toremifene was reduced by 87% (P < .001), Cmax by 55% (P < .001), and t1/2 by 44% (P < .01) with rifampin. During the rifampin phase, the AUC of N-demethyltamoxifen was 38% (P < .001) and the AUC of N-demethyltoremifene was 20% (P < .01) of that during the placebo phase. CONCLUSIONS: Rifampin markedly reduces the plasma concentrations of tamoxifen and toremifene by inducing their CYP3A4-mediated metabolism. Concomitant use of rifampin or other potent inducers of CYP3A4 with tamoxifen and toremifene may reduce the efficacy of these antiestrogens.

Tamoxifen metabolites in patients on long-term adjuvant therapy for breast cancer.

Serum concentrations of tamoxifen, 4-OH-tamoxifen, N-desmethyltamoxifen, and metabolites E and Y were assayed to assess the variation of tamoxifen-metabolism during short-term and long-term endocrine treatment for breast cancer. Once steady-state was achieved, serum levels of tamoxifen and its metabolites in individual patients were stable in the short (10 weeks) and long term (over 7 years) (coefficient of variation [CV], 10-15%), but the variation between individuals (CV 50-70%) was high. Serum tamoxifen and N-desmethyltamoxifen levels were not correlated with indices of obesity. Thus this does not explain the large variation between individuals. In addition to the metabolites that were measured, 4-hydroxy-N-desmethyltamoxifen was tentatively identified in patients' serum. Overall, this study demonstrated that the metabolites of tamoxifen are stable (i.e. no metabolic tolerance) for up to 10 years of drug administration.

Pharmacokinetic profile of intramuscular fulvestrant in advanced breast cancer.

OBJECTIVE: To characterise the pharmacokinetics of a long-acting formulation of fulvestrant following intramuscular administration of single and multiple doses. STUDY DESIGN: Pharmacokinetic investigations of single and multiple doses of fulvestrant were conducted within two global phase III efficacy studies that compared intramuscular fulvestrant with oral anastrozole in postmenopausal women with hormone-sensitive advanced breast cancer (study 0020, conducted in Europe, Australia and South Africa, and study 0021, conducted in North America). METHODS: Patients received once-monthly intramuscular injections of fulvestrant 250 mg (1 x 5 mL for < or =21 months in study 0020; 2 x 2.5 mL for < or =30 months in study 0021). Serial blood samples were collected for the first 28 days after the initial dose and immediately prior to all subsequent monthly doses. Plasma fulvestrant concentrations were determined by high-performance liquid chromatography-tandem mass spectrometry. PATIENTS: Twenty-six (study 0020) and 193 (study 0021) postmenopausal women, comprising the pharmacokinetic subgroups of the phase III efficacy trials, were studied. Patients had shown disease progression or recurrence following previous hormonal therapy for advanced disease or had relapsed after adjuvant endocrine therapy with a nonsteroidal antiestrogen. OUTCOME MEASURES AND RESULTS: For single-dose fulvestrant 250 mg, area under the concentration-time curve from time zero to 28 days (AUC(28)), maximum observed plasma concentration (C(max)), minimum observed plasma concentration at 28 days (C(min)) and time to maximum plasma concentration (t(max)) were determined. For multiple-dose fulvestrant 250 mg once monthly, steady-state trough concentrations (C(trough)) were determined. Plasma fulvestrant concentrations reached a peak at a median of 7 days (range 2-8 days) postdose, and declined biexponentially with a slower phase commencing approximately 2-3 weeks postdose. Intersubject variability in C(max) and AUC(28) was approximately 6-fold and 4-fold, respectively. Mean parameters for single-dose fulvestrant were: AUC(28), 148 microg. day/L; C(max), 8.2 microg/L; C(min), 2.6 microg/L; t(max), 7.0 days. Geometric mean C(trough) increased from 2.57 to 6.15 microg/L (study 0020) and from 2.38 to 6.52 microg/L (study 0021) over the first 6 months, reaching steady-state concentrations of approximately 6-7 microg/L (study 0020) or 9 microg/L (study 0021). Preliminary pharmacokinetic analysis, using a naive pooled data approach, suggests that observed single- and multiple-dose plasma profiles can be adequately described with a two-compartment kinetic model. Model-generated steady-state AUC(28) values were approximately 300 microg. day/L. CONCLUSIONS: The intramuscular formulation of fulvestrant displays predictable kinetics and approximately 2-fold accumulation on administration once monthly. At the proposed therapeutic dosage (250 mg once monthly), plasma fulvestrant concentrations are maintained within a narrow range throughout the administration interval, thus ensuring stable systemic drug exposure during long-term treatment.

Hypothalamic, pituitary and uterine cytoplasmic and nuclear oestrogen receptors and their relationship to the serum concentration of tamoxifen and its metabolite, 4-hydroxytamoxifen, in the ovariectomized rat.

High-affinity oestrogen receptors were measured in the cytosol and nuclei prepared from the hypothalamus, pituitary gland and uterus of the ovariectomized rat up to 16 days after a single dose of tamoxifen or 4-hydroxytamoxifen. Tamoxifen produced a dose-related fall in the concentration of cytosol receptors in the hypothalamus, pituitary gland and uterus. Minimum values were observed after 24 h; cytosol receptor concentrations were restored slowly and only reached expected control values between 4 and 8 days and 2 and 4 days for 7.0 mg/kg and 0.7 mg/kg doses of tamoxifen respectively. The nuclear receptor changes were inversely related to the cytosol receptor changes, except that hypothalamic nuclear receptor concentrations after 0.7 mg tamoxifen/kg were not changed. 4-Hydroxytamoxifen (0.14 mg/kg) depleted cytosol and raised nuclear oestrogen receptors in the pituitary gland and uterus. Receptor concentrations had returned to the expected control values by day 4. Oestrogen receptor concentrations in the hypothalamus were unchanged. The apparent resistance of the receptor system in the hypothalamus to translocation by tamoxifen and 4-hydroxytamoxifen was probably due to the blood-brain barrier since the apparent affinity of tamoxifen for the cytosol receptor was similar for all three tissues (dissociation constant 4 nmol/l). Serum concentrations of tamoxifen and 4-hydroxytamoxifen measured after a single dose of 7.0 mg tamoxifen/kg were maximal after 24 h and undetectable by 4 days, at which time nuclear and cytosol receptor levels were still changed. Concentrations of 4-hydroxytamoxifen were approximately one-third those of tamoxifen. The results suggest that the receptor changes after tamoxifen are not simply related to the serum concentration of tamoxifen and its metabolites and that the retention of ligand within the target tissue may be an important determinant.

Pharmacokinetics of toremifene and its metabolites in patients with advanced breast cancer.

A multicenter phase I pharmacokinetic study of a new triphenylethylene antiestrogen, toremifene, was examined in 70 patients with advanced breast cancer. Patients were randomized to receive single daily oral doses of either 10, 20, 40, 60, 200, or 400 mg for 8 weeks. Plasma toremifene and its major metabolites. N-desmethyltoremifene and 4-hydroxytoremifene, were determined weekly during therapy and at 0, 7, 14, and 21 days after the discontinuation of therapy. The time to reach steady-state plasma concentrations was between 1 and 5 weeks, with steady-state being achieved earlier (1-2 weeks) at daily doses of 200 and 400 mg. The time to peak concentration following oral doses of toremifene ranged from 1.5 to 4.5 h. The terminal half-life of elimination was 5.0, 6.0, and 5.0 days for toremifene, desmethyltoremifene, and 4-hydroxytoremifene, respectively. Plasma concentrations of 4-hydroxytoremifene were detectable only at high doses (200 and 400 mg/day) of toremifene. The results of this phase I pharmacokinetic study show that toremifene has metabolic and kinetic patterns that are similar to those previously reported with tamoxifen.

Phase I study of percutaneous 4-hydroxy-tamoxifen with analyses of 4-hydroxy-tamoxifen concentrations in breast cancer and normal breast tissue.

4-OH-tamoxifen is an active metabolite of tamoxifen that is detectable in the serum and tumour tissue of patients treated by oral tamoxifen. As this metabolite penetrates through the skin, it is possible to compare percutaneous 4-OH-tamoxifen (4-OH-TAM) and oral tamoxifen treatments. We report herein a randomized study of percutaneous 4-OH-TAM versus oral tamoxifen in women with breast cancer. This pharmacology study was designed to compare the 4-OH-TAM concentration in breast cancer and normal breast tissue according to the route and dose used for administration of tamoxifen after a 3-week period prior to surgery and tissue sampling. Women were randomized into one of the five following groups: group I, oral tamoxifen given at 10 mg twice a day; group II, 4-OH-TAM delivered percutaneously at 0.5 mg day to both breast areas; group III, 4-OH-TAM applied percutaneously at 1 mg/day to both breast areas; group IV, 4-OH-TAM delivered percutaneously at 1 mg/day to a large cutaneous area excluding the breasts; and group V, 4-OH-TAM applied percutaneously at 2 mg/day to a large skin area excluding the breasts. 4-OH-TAM plasma and tissue concentrations were significantly higher in the oral tamoxifen group as compared with either the high- or the low-dose percutaneous 4-OH-TAM group. In group II, percutaneous 4-OH-TAM treatment resulted in tissue concentrations of 1,446 and 352 pg/g in tumour tissue and normal breast tissue, respectively. In group I these concentrations were as follows: tumour tissue, 12, 453 pg/g; and normal tissue, 10,214 pg/g. 4-OH-TAM concentrations in tumour tissue and normal breast tissue did not significantly differ in any group. In the oral group we observed classic effects on coagulation and lipid metabolism when pre- and post-treatment values of these biological variables were compared, whereas no difference was observed in the percutaneous group. Although percutaneous administration of 4-OH-TAM led to a low plasmatic concentration of this active metabolite, the breast tissue concentration remained lower than those observed after oral tamoxifen treatment. Therefore, at the doses described in this study, percutaneous 4-OH-TAM cannot be proposed as an alternative tamoxifen treatment.

A new triphenylethylene derivative, TAT-59; hormone receptors; insulin-like growth factor 1; and growth suppression of hormone-dependent MCF-7 tumors in athymic mice.

TAT-59 ((E)-4-[1-[4-[2-(dimethylamino)ethoxy]-phenyl]-2-(4- isopropyl)phenyl-1-butenyl]-phenyl-monophosphate) treatment was performed on hormone-dependent MCF-7 tumors in athymic mice. TAT-59 given at 1, 5, and 20 mg/kg inhibited the estrogen-stimulated growth of MCF-7 tumors in athymic mice in a dose-dependent fashion. The most clear decrease in tumor growth was shown in the TAT-59 alone group, although it was not dramatic. Average serum concentrations of DP-TAT-59((Z)-[1-[4-[2-(dimethylamino)- ethoxy]phenyl]-2-(4-isopropyl)phenyl-1-butenyl]-4-hydroxybenzene) and DM-DP-TAT-59(desmethyl-DP-TAT-59), metabolites of TAT-59, increased in a dose-dependent manner. Much higher levels of DP-TAT-59 and DM-DP-TAT-59 were shown in tumors (target tissues of estrogen) as compared with muscles (nontarget tissues of estrogen) or serum. A serum concentration of DP-TAT-59 or DM-DP-TAT-59 corresponding to the physiologic levels of serum estradiol in premenopausal women was sufficient to inhibit the estrogen-stimulated growth of MCF-7 tumors in mice. TAT-59 induced a dose-dependent increase in estrogen receptor levels in the MCF-7 tumors. In contrast, it prevented the estradiol (E2)-induced increase in progesterone receptor levels in a dose-dependent manner. Insulin-like growth factor 1 levels measured in the MCF-7 tumors significantly decreased in the TAT-59 alone group and in the no treatment group as compared with the E2 alone group. These results show the pronounced antiestrogenic action of TAT-59 on hormone-dependent MCF-7 tumors in athymic mice.

Determination of panomifene in human plasma by high-performance liquid chromatography.

An ion-pair HPLC method was developed for the determination of the antiestrogenic drug panomifene, (E)-1,2-diphenyl-1-(4-[2-(2-hydroxyethylamino)ethoxy]phenyl)-3,3,3 - trifluoropropene, in human plasma. Tamoxifen, 20 ng in 1 ml of plasma, was used as an internal standard. The compounds were isolated from plasma by liquid-solid extraction. Fluorescence detection was achieved by on-line photochemical conversion of the compounds into highly fluorescent phenanthrene derivatives. The sensitivity of the method was 1 ng/ml. The within-day and between-day precision, linearity, extraction recovery and stability of panomifene in plasma and in deproteinized plasma were determined for validation of the method. The method is suitable for measuring plasma levels of panomifene and tamoxifen and for pharmacokinetic studies.

Atmospheric pressure photoionization liquid chromatographic-mass spectrometric determination of idoxifene and its metabolites in human plasma.

This paper describes a comparison between atmospheric pressure chemical ionization (APCI) and the recently introduced atmospheric pressure photoionization (APPI) interface for the LC-MS determination of idoxifene and its major metabolite, SB245419 (SB19), in human plasma. The results indicate that analyte response in APPI is highly dependent on the solvent composition, especially to water in the mobile phase. Other parameters investigated are the mobile phase flow-rate, the chemical noise, and signal suppression by matrix interferences. APPI appears to be six to eight times more sensitive than APCI for idoxifene and its SB245419 metabolite; the response for the SB245420 metabolite is considerably better than for APCI conditions, but still not sufficient for trace level pharmacokinetic determinations in human plasma. The LOQ for the parent drug and its major metabolite were 10 and 25 ng/ml, respectively, in human plasma. From post-column infusion experiments we conclude that there is little difference in matrix suppression between APCI and APPI. From these studies we suggest APPI may be an additional tool in pharmaceutical LC-MS applications.

Rat and human embryo and post-natal sera contain a potent endogenous competitor of estrogen-rat alpha-fetoprotein interactions.

A highly active inhibitor of the binding of estrone and estradiol-17beta to rat alpha-fetoprotein is demonstrated for the first time in embryo, immature and adult rat sera as well as in fetal and adult human sera. The competitive character and the narrow specificity of this inhibition effect is shown. The major compound responsible for this activity is isolated by successive column Sephadex LH20 and thin layer chromatography: it is characterized as a nonpolar, nonphenolic, dialysable and thermostable substance, unreactive towards anti-estrone and anti-estradiol-17beta antibodies. The possible biological role of an endogenous non-estrogen ligand of rodent fetoproteins is discussed.

Effect of exposure to 3,3',4,4',5-pentachlorobiphenyl (PCB 126) throughout gestation and lactation on development and spatial delayed alternation performance in rats.

There is evidence that polychlorinated biphenyl (PCB) congeners have differential effects on endpoints of neurotoxicity depending on their chemical structure: specifically, that ortho-substituted congeners are neurotoxic whereas coplanar (dioxin-like) congeners are relatively inactive in producing neurotoxic effects. The effects of the coplanar congener 3,3',4,4',5-pentachlorobiphenyl (PCB 126) on developmental endpoints, hematology, serum biochemistry, and performance on a spatial delayed alternation task were assessed in Long-Evans rats. Dams were dosed with 0, 0.25, or 1.0 microg/kg/day Monday to Friday beginning 5 weeks before and continuing through gestation and lactation. The first 2-week breeding period produced 10, 8, and 13 litters in the three dose groups, respectively. Breeding females from the control and low-dose group that did not conceive were rebred after 76 days of dosing, producing 7 and 6 litters, respectively. Reduction in weight gain from birth to weaning at 21 days of age (DOA) was observed in both dose groups of Cohort 1 but not in Cohort 2. Males in Cohort 1 exhibited a slight decrease in anogenital distance normalized for weight. Changes in hematological and some serum biochemical parameters were observed in the pups at DOA 21 and/or 60. PCB 126 was detected in fat sampled at both DOA 21 and 60. PCB 126 was not detected in brain samples at 60 DOA in any group; analysis of Cohort 2 at DOA 21 revealed levels in the treated group about 1/100 of those in fat. On the spatial delayed alternation task, there was no convincing evidence for impairment as a result of PCB exposure, as assessed by overall accuracy of performance and measures of perseverative and other types of inappropriate responding. These data provide further evidence for the lack of neurotoxicity of dioxin-like PCB congeners. However, assessment of performance on additional behavioral indices is required before definitive conclusions may be drawn.

Estrogen mitogenic action. ii. negative regulation of the steroid hormone-responsive growth of cell lines derived from human and rodent target tissue tumors and conceptual implications.

In an accompanying report (Moreno-Cuevas, J. E.; Sirbasku, D. A., In Vitro Cell. Dev. Biol.; 2000), we demonstrated 80-fold estrogen mitogenic effects with MTW9/PL2 rat mammary tumor cells in cultures supplemented with charcoal-dextran-treated serum. All sera tested contained an estrogen reversible inhibitor(s). The purpose of this report is to extend those observations to additional sex steroid-responsive human and rodent cell lines. Every line tested showed a biphasic response to hormone-depleted serum. Concentrations of < or = 10% (v/v) promoted substantive growth. At higher concentrations, serum was progressively inhibitory. With estrogen receptor-positive (ER+) human breast cancer cells, rat pituitary tumor cells, and Syrian hamster kidney tumor cells, 50% (v/v) serum caused significant inhibition, which was reversed by very low physiologic concentrations of estrogens. This same pattern was observed with the steroid hormone-responsive LNCaP human prostatic carcinoma cells. Because steroid hormone mitogenic effects are now easily demonstrable using our new methods, the identification of positive results has nullified our original endocrine estromedin hypothesis. We also evaluated autocrine/paracrine growth factor models of estrogen-responsive growth. We asked if insulin-like growth factors I and II, insulin, transforming growth factor alpha, or epidermal growth factor substituted for the positive effects of estrogens. Growth factors did not reverse the serum-caused inhibition. We asked also if transforming growth factor beta (TGFP) substituted for the serum-borne inhibitor. TGFbeta did not substitute. Altogether, our results are most consistent with the concept of a unique serum-borne inhibitor as has been proposed in the estrocolyone model. However, the aspect of the estrocolyone model related to steroid hormone mechanism of action requires more evaluation. The effects of sex steroids at picomolar concentrations may reflect mediation via inhibitor "activated" intracellular signaling pathways.