Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.3.1 (alkaline phosphatase)
47,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of estrogens on the growth and function of primary rabbit kidney proximal tubule (RPT) cells have been examined in hormonally defined phenol red-free medium. 17beta-estradiol was observed to stimulate growth at dosages as low as 10(-10) M. The growth stimulatory effects of 17beta-estradiol were mitigated in the presence of hydrocortisone, suggesting that these two steroid hormones acted at least in part by common mechanisms. The effects of other steroids known to interact with the estrogen receptor were examined. Alpha estradiol was found to be growth stimulatory over a concentration range of 10(-9) to 10(-8) M, albeit to a lower extent than beta estradiol. In addition, the anti-estrogen tamoxifen was also growth stimulatory (unlike the case with the human mammary tumor cell line MCF-7). The effects of several metabolic precursors of 17beta-estradiol were examined, including testosterone, which was growth stimulatory, and progesterone, which was growth inhibitory. The growth stimulatory effects of 17beta-estradiol, alpha estradiol, and tamoxifen could possibly be explained by their interaction with an estrogen receptor. Indeed, metabolic labelling and immunoprecipitation studies indicated the presence of such an estrogen receptor in the primary cultures. The rate of biosynthesis of the estrogen receptor was found to be affected by the presence of exogenously added 17beta-estradiol. 17beta-estradiol was also observed to increase the activity of two brush border enzymes, alkaline phosphatase and gamma glutamyl transpeptidase, during the growth phase of the primary cultures.
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PMID:Response of primary rabbit kidney proximal tubule cells to estrogens. 988 88

Sulfation is an important conjugation reaction in the metabolism of steroids. Steroids sulfates do not interact with the appropriate hormone receptors; additionally, the presence of the charged sulfate moiety increases the aqueous solubility and excretion of most steroids. Estrogen sulfotransferase (EST) is the major form of human cytosolic ST involved in the conjugation of estrogens. EST is important in the inactivation of beta-estradiol (E2) during the luteal phase of the menstrual cycle. EST has a significantly higher affinity for the sulfation of E2 and 17alpha-ethinylestradiol (EE2) than for other potent estrogens such as diethylstilbestrol (DES) and equine estrogens. The ability of EST to sulfate these estrogenic compounds at physiologic concentrations is important in regulating their activation of the ER in estrogen responsive cells. Human Ishikawa endometrial adenocarcinoma (ISH) cells possess an estrogen receptor (ER)-regulated alkaline phosphatase (AlkPhos) which is used to assay ER activation. To study the effects of EST activity on the ER activation of different estrogenic compounds, ISH cells were stably transformed with an EST expression vector. Dose-response curves for the induction of AlkPhos activity by the different estrogenic compounds were generated with EST/ISH and control pcDNA/ISH cells. EST/ISH cells were 200-fold less sensitive to E2 and EE2 than were control cells. No differences were observed in the dose response curves for DES between EST/ISH and pcDNA/ISH cells. EST/ISH cells were approximately 3-10-fold less sensitive to the equine estrogens equilin and 17-equilin as compared to control cells. The ability of EST to decrease the ER activation of an estrogen correlates with the sulfation of these compounds at nanomolar concentrations by EST/ISH and pcDNA/ISH ISH cells. These results indicate that EST is capable of efficiently inactivating E2 and EE2 but is significantly less effective in inhibiting the ER binding of other potent estrogenic compounds.
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PMID:Regulation of estrogen activity by sulfation in human Ishikawa endometrial adenocarcinoma cells. 1036 11

A new class of compounds known as selective estrogen receptor modulators (SERMs) may possess the optimal combination of characteristics desirable in a drug designed for use in postmenopausal women. Among this class of compounds, raloxifene is the most studied and is currently available for clinical use in some countries for the prevention of osteoporosis in post-menopausal women. Raloxifene is a non-steroidal benzotiophene derivative shown to prevent bone loss at axial and appendicular sites and reduce serum cholesterol, like estrogen, in oophorectomized rats and in postmenopausal women. In animal models, unlike estrogen, raloxifene does not stimulate breast or uterine tissues. These appealing attributes make raloxifene a potential treatment for osteoporosis and other menopause related risks in middle aged and elderly women. Multicenter studies have been performed in early postmenopausal women, randomly assigned to receive raloxifene 30, 60, or 150 mg/day or placebo. All subjects received a calcium supplement. Bone mineral density, which was measured twice a year over 24 months by dual X-ray absorptiometry, decreased significantly at all skeletal sites with placebo, and significantly increased with raloxifene at the spine, hip, and total body at the three doses. At 24 months, the mean increase with raloxifene 60 mg compared with placebo was 2.4% at the lumbar spine and at the total hip, and 2% at the total body. Markers of bone formation (serum osteocalcin and bone specific alkaline phosphatase) and of resorption (urinary CrossLaps) decreased significantly to the premenopausal range within 3-6 months of treatment with raloxifene. In addition, total serum and low-density lipoprotein cholesterol decreased significantly in all raloxifene therapy groups in a dose-related fashion. Serum HDL-cholesterol and triglycerides were not significantly changed by therapy. The most commonly observed side-effect was hot flushes, with patients taking raloxifene reporting a slightly higher rate of flushes (25%) than those on placebo (18%). This adverse event usually occurred within the first few months of therapy, was generally mild, and did not result in excess study dropout (raloxifene 1.5%, placebo 2.1%). Preliminary 2-year data indicated that raloxifene is not associated with an increased risk of breast cancer. In summary, the clinical efficacy and safety of raloxifene is very promising and this compound will offer a particularly attractive choice for postmenopausal women.
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PMID:Clinical efficacy of raloxifene in postmenopausal women. 1042 20

A population of estrogen receptor-alpha (ER alpha) proteins, located at the plasma membrane, is postulated to mediate the rapid, nongenomic responses of GH3/B6/F10 pituitary cells to estrogen. To demonstrate the presence of ER alpha at the plasma membrane and to distinguish this receptor population from that in the nucleus, GH3/B6/F10 cells were first prepared in 2% paraformaldehyde/0.1% glutaraldehyde in PBS (P/G) without detergent, then exposed to one of several antibodies (Abs) raised against nuclear ER alpha. Ab binding was visualized as a fluorescent/chromagenic reaction product catalyzed by avidin-biotin-complexed alkaline phosphatase. With P/G fixation, Abs could only access antigens at the cell surface, as evidenced by the inability of 70K mol wt dextrans to permeate cells and the absence of intracellular staining by Abs to cytoplasmic or nuclear antigens. ER alpha Abs generated membrane, but not nuclear, staining in P/G-fixed cells; nuclear receptor labeling could only be detected in detergent-treated cells. Specificity of staining for ER alpha was confirmed by three approaches: first, treatment with an antisense oligodeoxynucleotide to nuclear ER alpha mRNA reduced immunolabeling of both membrane and nuclear ER alpha; second, labeling by two Abs raised against different ER alpha oligopeptides was neutralized by competing peptide; third, six Abs (ER21, H226, R4, H222, MC20, and C542) that recognize unique epitopes on rodent ER alpha produced immunolabeling, but neither primate-specific ER alpha Ab nor Ab to ER beta caused staining. In addition to demonstrating the plasma membrane ER alpha in GH3/B6/F10 cells, this method should be applicable to other cell types that exhibit nongenomic responses to estrogen or other steroid hormones.
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PMID:Estrogen receptor-alpha detected on the plasma membrane of aldehyde-fixed GH3/B6/F10 rat pituitary tumor cells by enzyme-linked immunocytochemistry. 1043 42

Ovariectomy in young, growing rodents results in decreased trabecular bone mineral density (BMD) and increased radial growth of the cortical bone. Both of these effects are reversed by treatment with estrogen. The aim of the present study was to determine the physiological role of estrogen receptor-beta (ERbeta) on bone structure and bone mineral content (BMC). The BMC was increased in adult (11 weeks old), but not prepubertal (4 weeks old), female ERbeta(-/-) mice compared with wild-type (WT) mice. This increase in BMC in females was not due to increased trabecular BMD, but to an increased cross-sectional cortical bone area associated with a radial bone growth. Male ERbeta(-/-) mice displayed no bone abnormalities compared with WT mice. Ovariectomy decreased the trabecular BMD to the same extent in adult female ERbeta(-/-) mice as in WT mice. The expression levels of osteoblast-associated genes - alpha1(I) collagen, alkaline phosphatase, and osteocalcin mRNAs - were elevated in bone from adult ERbeta(-/-) females compared with WT mice. These observations provide a possible explanation for the increased radial bone growth seen in female mutants, suggesting a repressive function for ERbeta in the regulation of bone growth during female adolescence. In summary, ERbeta is essential for the pubertal feminization of the cortical bone in female mice but is not required for the protective effect of estrogens on trabecular BMD.
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PMID:Increased cortical bone mineral content but unchanged trabecular bone mineral density in female ERbeta(-/-) mice. 1051 Mar 30

Raloxifene, a selective estrogen receptor modulator (SERM), has been shown to improved bone mineral density (BMD) and serum lipid profiles in healthy postmenopausal women. The objective of this study was to examine the effects of raloxifene on BMD, biochemical markers of bone metabolism and serum lipids in postmenopausal women with low bone density or osteoporosis. This Phase II, multicenter, 24-month, double-masked study assessed the efficacy and safety of raloxifene in 129 postmenopausal women (mean age +/- SD: 60.2 +/- 6.7 years) with osteoporosis or low bone density (baseline mean lumbar spine BMD T-score: -2.8). Women were randomly assigned to one of three treatment groups: placebo, 60 mg/day raloxifene-HCl (RLX 60) or 150 mg/day raloxifene-HCL (RLX 150) and concomitantly received 1000 mg/day calcium and 300 U/day vitamin D3. At 24 months, BMD was significantly increased in the lumbar spine (+3.2%), femoral neck (+2.1%), trochanter (+2.7%) and total hip (+1.6%) in the RLX 60 group compared with the placebo group (p < 0.05). The RLX 150 group had increases in BMD similar to those observed with RLX 60. A greater percentage of raloxifene-treated patients, compared with those receiving placebo, had increased BMD (p < 0.05). Serum bone-specific alkaline phosphatase activity, serum osteocalcin, and urinary type I collagen:creatinine ratio were significantly decreased in the RLX-treated groups, compared with the placebo group (p < 0.01). RLX 60 treatment significantly decreased serum levels of triglycerides, and total- and LDL-cholesterol levels (p < 0.01). The rates of patient discontinuation and adverse events were not significantly different among groups. In this study, raloxifene increased bone density, decreased bone turnover, and improved the serum lipid profile with minimal adverse events, and may be a safe and effective treatment for postmenopausal women with osteoporosis or low bone density.
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PMID:Treatment of postmenopausal women with osteoporosis or low bone density with raloxifene. Raloxifene Study Group. 1069 84

Clinical course in hepatocellular carcinoma may be very different. We prospectively evaluated 96 patients with hepatocellular carcinoma unsuitable for radical therapy to investigate factors that could influence survival. Clinical, pathologic, and molecular data of patients were analyzed by univariate and multivariate analysis. The overall actuarial probability of survival at year 1, 2, 3, 4, 5, and 6 was 72%, 41%, 38%, 24%, 20%, and 9%. At univariate analysis, alpha-fetoprotein (AFP) (P =.0082); alkaline phosphatase (P =.0281); bilirubin (P =.0076); etiology (P =.0001); increment of tumor mass at month 3 (P =.0051); type of estrogen receptor (ER) in the tumor (P =.0000); prothrombin time (P =.0003); and portal vein thrombosis (P =.0000) had prognostic significance. At multivariate analysis, only type of ER (P =.0000) and bilirubin (P =.0030) showed independent predictive value for mortality. Survival was significantly longer in patients with wild-type estrogen receptors (P =.0000). Cumulative probability of survival at year 1, 2, 3, 4, 5, and 6 was 94%, 66%, 52%, 43%, 35%, and 18% for wild-type and 51%, 21%, 16%, and 9% for variant estrogen receptors (no patients alive after 4 years). Hepatitis B surface antigen (HBsAg)-positive patients with variant ERs had a median survival of 8 months versus 45 months in anti-hepatitis C virus-positive patients with wild-type ERs (P =.0001). In conclusion, (1) the presence of variant liver ER transcripts in the tumor was the strongest negative predictor of survival in inoperable hepatocellular carcinoma; (2) their presence was associated with spontaneous survival significantly worse than in patients with wild-type estrogen receptors; and (3) HBsAg-positive patients with variant receptors were characterized by the worst survival.
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PMID:Natural history of inoperable hepatocellular carcinoma: estrogen receptors' status in the tumor is the strongest prognostic factor for survival. 1091 29

Evidence for the role of estrogen in male bone metabolism has been confirmed by studies on a man with a genetic defect in the estrogen receptor as well as men with aromatase defects. All exhibited tall stature, delayed epiphysial closure, decreased bone density and increased bone turnover. Estrogen is likely to affect bone turnover in men throughout life; therefore, we hypothesized that older men would show decreased bone resorption in response to estrogen therapy. To test our hypothesis, fourteen community-dwelling men with osteopenia of the femoral neck were treated for 9 weeks with micronized estradiol, 1 mg/d, a dose which is effective in postmenopausal women. Each subject served as his own control. Markers of bone resorption, N-terminal collagen crosslinks (NTX) and C-terminal collagen crosslinks (CTX) and markers of bone formation, osteocalcin (OC) and bone specific alkaline phosphatase (BSAP) were measured every 3 weeks during a 9-week treatment period and 9 weeks post-treatment. Sex hormones, gonadotrophins and calciotropic hormones were measured at baseline, 9 weeks on treatment and 9 weeks post- treatment. After 9 weeks of treatment, estradiol and estrone levels increased significantly by greater than 6-fold and 15-fold, respectively. SHBG levels increased significantly by 17%. Testosterone and free testosterone levels decreased significantly by 27% and 34%, respectively. Markers of bone resorption showed wide variation at baseline and while on treatment. There was no correlation between changes in bone markers and changes in estrogen levels. During treatment, 11 patients showed a decrease of NTX or CTX, but three showed an increase. These three and one other subject had high initial levels of FSH and LH, suggesting some degree of primary gonadal failure, which decreased during estrogen therapy. Thus, the change in NTX (and CTX) after 9 weeks of E2 treatment was correlated with initial FSH (r= -.66, p= .01) and LH (r= -.73, p= .003) values. In addition, the largest decrease in free testosterone at 9 weeks was correlated with the higher values for NTX, CTX and BAP (r=-0.66, -0.68, -0.70 respectively; p< or =.01 for each of the markers). Treatment was generally well tolerated. Side effects of treatment were minimal, and included breast tenderness and decreased libido which reversed after treatment. We conclude that it is feasible to give low dose estrogen to healthy older men, but that the effects on bone turnover are not consistent. Changes in central feedback and in endogenous sex hormone production may alter the response of bone turnover to exogenous estrogen in this population.
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PMID:The effect of short-term treatment with micronized estradiol on bone turnover and gonadotrophins in older men. 1101 3

Trimegestone (TMG) is a novel 19-norpregnane progestin under development for hormone replacement therapy and oral contraception. The objective of the current study was to characterize the potency and steroid receptor selectivity of TMG in several in vitro assays and to compare its activity to that of medroxyprogesterone acetate (MPA). TMG and MPA had a similar competitive binding affinity for human and rabbit progesterone receptor (PR). However, TMG had a significantly higher affinity for rat PR (IC(50) = 3.3 nM) than MPA (IC(50) = 53.3 nM). In T47D cells, both compounds increased alkaline phosphatase activity and cell proliferation with comparable potencies (EC(50s) of 0.1 nM and of 0.02 nM, respectively). To further characterize the progestational activity and steroid receptor selectivity, we established an immortalized human endometrial stromal cell line (HESC-T). This cell line lacks endogenous estrogen receptor (ER) and PR but does have functional glucocorticoid receptors (GR). When ER is transiently expressed in the cells, 17beta-estradiol (E(2)) induces PR, allowing the study of PR-regulated genes. In HESC-T cells expressing exogenous ER, and therefore PR, both TMG and MPA increased HRE-tk-luciferase activity tenfold with an EC(50) of 0.2 nM. In HESC-T cells without exogenous ER, and therefore no PR, TMG did not induce HRE-tk-luciferase activity, whereas MPA induced the reporter activity with an EC(50) of about 10 nM. This MPA-induced reporter activity is believed to be mediated through GR. The steroid receptor selectivity of TMG was further evaluated using the HRE-tk-luciferase assay in the human lung carcinoma cell line A549, which contains GR but no PR. In these cells TMG had no effect on luciferase activity, whereas MPA increased the reporter activity in a dose-dependent manner with an EC(50) of approximately 30 nM. Furthermore, HRE-tk-luciferase assay in mouse fibroblast cell line L929, which expresses androgen receptor (AR) but no PR, showed that TMG had weak antiandrogenic activity whereas MPA had androgenic activity. In summary, data from several in vitro assays demonstrate that TMG is a potent progestin with a better receptor selectivity profile than MPA.
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PMID:In vitro characterization of trimegestone: a new potent and selective progestin. 1110 70

The cytotoxicity of hydroxyurea (HU), currently used to combat various cancers, sickle cell anemia and human immunodeficiency infection, was assessed by exposing decidualized and pregnant uteri of Sprague-Dawley rats to this drug. Consecutive daily doses of HU (500 mg/kg(-1)) for 4 days were injected subcutaneously during decidualization when proliferation of the deciduoma was biochemically analyzed on pseudopregnancy day 9, or injected intraperitoneally during pregnancy when uterine developmental processes were evaluated on gestation day 16. Hydroxyurea displayed prominent antiproliferative effects on decidual growth. These actions were comparable to significantly impaired (P<0.001) developmental responses (increases in post-implantation losses, in resorbed fetuses and in reduced fetal and placental weights) during pregnancy. The cellular components inhibited by HU were DNA, protein, nitric oxide synthase, a matrix metalloproteinase and decidual prolactin-related protein mRNA (P<0.05). Steroid-related endocrine events (serum progesterone concentrations, estrogen receptor and mRNA levels) were unaffected by HU, implying direct cellular action by the drug. Interestingly, endometrial alkaline phosphatase bioactivity was enhanced by HU (P<0.05). Subsequently, the reproductive toxicity of HU was apparently related to mitogenic and differentiation-induced endometrial cellular activities.
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PMID:Hydroxyurea inhibition of cellular and developmental activities in the decidualized and pregnant uteri of rats. 1113 71


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