Skeletal effects of calcitonin in ovariectomized rats

Although calcitonin (CT) has been shown to be effective for the prevention of bone loss in early postmenopausal women, the skeletal effects of the hormone specifically during the early stages of estrogen deficiency have not been characterized histomorphometrically to date. The current study involves use of the ovariectomized (OVX) rat as an animal model for early postmenopausal bone loss to perform such a histomorphometric analysis. One group of OVX rats was injected sc with salmon CT on alternate days for a 6-week period. Additional groups of OVX and sham-operated control rats were treated with vehicle alone. In comparison to control rats, the proximal tibia of vehicle-treated OVX rats were characterized by a 3-fold decrease in cancellous bone volume and significant increases in osteoblast surface (+200%), osteoclast surface (+143%), mineralizing surface (+111%), mineral apposition rate (+36%), bone formation rate (+181%), and longitudinal bone growth (+38%). In contrast, treatment of OVX rats with CT normalized tibial cancellous bone volume and significantly decreased all of the above cellular- and fluorochrome-based indices of bone turnover to near control levels. The results indicate that CT treatment depresses bone turnover and prevents the development of osteopenia in OVX rats. These findings are consistent with the bone protective effect of CT in early postmenopausal women and further support the OVX rat as an animal model for the preclinical evaluation of prophylactic treatments for postmenopausal bone loss.     

Sequential treatment with basic fibroblast growth factor and PTH is more efficacious than treatment with PTH alone for increasing vertebral bone mass and strength in osteopenic ovariectomized rats

The study was designed 1) to determine whether treatment with basic fibroblast growth factor (bFGF) and PTH is more efficacious than treatment with PTH alone for increasing bone mass and strength and improving trabecular microarchitecture in osteopenic ovariectomized rats, and 2) to assess whether prior and concurrent administration of the antiresorptive agents estrogen and risedronate suppresses the bone anabolic response to treatment with bFGF alone and sequential treatment with bFGF and PTH. Three-month-old female Sprague Dawley rats were ovariectomized (OVX) or sham-operated (sham) and maintained untreated for 1 yr. Baseline sham and OVX rats were killed at this time (15 months of age). Groups of rats were injected sc with estrogen (10 microg/kg, 4 d/wk), risedronate (5 microg/kg, 2 d/wk), or vehicle. At the end of the second week of antiresorptive treatment, catheters were inserted into the jugular veins of all rats, and vehicle or bFGF at a dose of 250 microg/kg was injected daily for 14 d. Three groups of rats were killed at the end of bFGF treatment. The remaining rats were continued on their respective antiresorptive therapy and injected sc with vehicle or synthetic human PTH-(1-34) at a dose of 80 microg/kg, 5 d/wk, for 8 wk. Lumbar vertebrae were processed for cancellous bone histomorphometry and biomechanical testing. Ovariectomy resulted in a decrease in vertebral bone mass and strength. Treatment of OVX rats for 14 d with bFGF markedly increased osteoblast surface, osteoid surface, and osteoid volume compared with vehicle treatment of sham and OVX rats. Furthermore, osteoid bridges were observed extending between preexisting trabeculae in bFGF-treated OVX rats. Prior and concurrent administration of estrogen and risedronate did not suppress these bone anabolic effects of bFGF. Treatment of OVX rats with PTH alone increased vertebral cancellous bone mass and strength to the level of vehicle-treated sham rats. Sequential treatment of OVX rats with bFGF and PTH further augmented vertebral bone mass and strength to a level above that observed in OVX rats treated with PTH alone. The improvements in bone mass and strength were associated with an increase in trabecular thickness in OVX rats treated with PTH alone and with an increase in trabecular thickness and node to terminus ratio, an index of trabecular connectivity, in OVX rats treated sequentially with bFGF and PTH. Cotreatment with estrogen and risedronate did not suppress the anabolic response of bone to bFGF and PTH. In fact, a trend for an even greater increase in cancellous bone mass and node to terminus ratio was observed in OVX rats treated with risedronate, bFGF, and PTH. These findings indicate that sequential treatment with bFGF and PTH is more efficacious than treatment with PTH alone for increasing bone mass and strength and improving trabecular microarchitecture in osteopenic OVX rats.     

Endocrine and pharmacological suppressors of bone turnover protect against osteopenia in ovariectomized rats

This study was designed to test the hypothesis that endocrine and pharmacological suppressors of bone turnover prevent the development of osteopenia during estrogen deficiency. Sham-operated control and ovariectomized (OVX) rats were treated intermittently with vehicle alone, estrogen, or the diphosphonate compounds etidronate disodium (EHDP) and NE-58095 [2-(3-pyridinyl)2-hydroxyethylidene-1,1-bisphosphonate disodium] for 35 or 70 days after surgery. Their proximal tibiae were processed undecalcified for quantitative bone histomorphometry. Vehicle-treated OVX rats were characterized by decreased cancellous bone volume and 3- to 4-fold increases in osteoblast surface, osteoclast surface, bone formation rate, and bone resorption rate. Treatment of OVX rats with estrogen and NE-58095 provided complete protection against bone loss and significantly depressed all of the above indices of bone turnover. OVX rats treated with EHDP exhibited at least partial protection against bone loss and decreased bone turnover. EHDP induced a mild mineralization defect, as indicated by a prolonged mineralization lag time at the tibial endocortical surface. The new diphosphonate compound NE-58095 did not impair bone mineralization. Our results indicate that endocrine and pharmacological suppressors of bone turnover prevent the development of osteopenia during the early stages of estrogen deficiency. If confirmed by clinical trials in humans, diphosphonate compounds may prove to be an alternative to estrogen for the prevention of postmenopausal bone loss.     

Dose-dependent effects of tamoxifen on long bones in growing rats: influence of ovarian status

Tamoxifen is a nonsteroidal antiestrogen which has been reported by various investigators to have estrogen agonist and antagonist effects on rat bone. These different interpretations may be due to differences in the ovarian status, estrogen levels, and/or tamoxifen levels of the rats. To address this issue, a dose response was determined for the effects of tamoxifen on bone histomorphometry in intact female and ovariectomized (OVX) rats. The results were compared with those obtained after treatment of OVX rats with estrogen alone or a combination of estrogen and tamoxifen. OVX resulted in increases in growth rate (weight gain) and periosteal bone formation rate and decreases in uterine weight and cancellous bone fractional volume (BV/TV). Treatment of OVX rats with estrogen resulted in dose-dependent decreases in growth rate and periosteal bone formation rate as well as dose-dependent increases in uterine weight and BV/TV. Similarly, tamoxifen treatment resulted in dose-dependent decreases in overall growth rate and periosteal bone formation rate in both OVX and intact rats. Tamoxifen treatment prevented the decrease in BV/TV after OVX, although the highest dose of tamoxifen resulted in a small decrease in BV/TV in intact female rats. In contrast to estrogen, tamoxifen treatment prevented the increase in uterine weight in intact female rats as well as the decrease in uterine weight in OVX rats. Tamoxifen treatment did not alter the effects of 17 beta-estradiol on the periosteal bone formation rate in OVX rats, but reduced the increase in BV/TV to values similar to those in intact rats. These results are consistent with tamoxifen behaving as a partial estrogen agonist on rat bone.     

17 beta-estradiol stimulates cancellous bone formation in female rats.

Estrogen is generally considered to maintain bone mass through suppression of bone resorption. We have previously demonstrated that administration of pharmacological doses of estrogen increases bone formation in rats. Because such high doses of estrogen might induce bone formation through some mechanism other than the estrogen receptor, we have now assessed the effect of more physiological doses of 17 beta-estradiol (E2) on bone formation. Adult female rats (13 weeks and 6 months old) administered E2 (1, 4, 40, 400, and 4 mg/kg daily for 17-21 days) showed a dramatic increase (5- to 8-fold) in cancellous bone formation, attributable to a combination of an increase in the proportion of bone surface actively undertaking bone formation, and an increase in the rate of mineral apposition. Significant anabolism was induced in 6-month-old rats by doses as low as 4 micrograms/kg and in 13-week-old rats by 40 micrograms/kg. Corresponding increases in the proportion of trabecular surface covered by osteoblasts were also observed. Histomorphometric indices of bone resorption were suppressed by estrogen. Estrogen administration caused an increase in bone volume up to 35% over controls, over a 21-day period. Stimulation of bone formation by estrogen showed a similar pattern of dose-responsiveness to recognized physiological targets of E2: suppression of longitudinal growth and uterine growth. These results suggest that stimulation of cancellous bone formation is a physiological action of E2 in the rat.     

Bone anabolic effects of basic fibroblast growth factor in ovariectomized rats

The purpose of this study was to characterize the bone anabolic effects of basic fibroblast growth factor (bFGF) in ovariectomized (OVX) rats. Female Sprague Dawley rats were subjected to ovariectomy or sham surgery at 3 months of age and maintained untreated for 2 months post surgery. Groups of OVX rats were then treated iv with bFGF at doses of 100 or 200 microg/kg day for 7 or 14 days. Another group of OVX rats and a group of sham-operated control rats were treated iv with vehicle alone for 14 days. Certain groups of bFGF-treated OVX rats were killed at 7 or 14 days after withdrawal of treatment. The right tibiae were processed undecalcified for quantitative bone histomorphometry. Vehicle-treated OVX rats were characterized by decreased cancellous bone volume associated with increased bone turnover. Treatment of OVX rats with bFGF strongly stimulated bone formation, as indicated by marked increases of at least a factor of 10 in osteoblast surface, osteoid surface, and osteoid volume. Furthermore, new osteoid spicules were observed within the marrow cavity of these animals. Osteoclast surface was markedly decreased in bFGF-treated OVX rats, but this finding may be secondary to the extensive osteoid surface. The strongest bone anabolic effects occurred in OVX rats treated with the higher dose of bFGF for 14 days, but these animals exhibited a bone mineralization defect, as evidenced by abundant osteoid and a lack of double fluorochrome labeling, despite markedly increased osteoblast surface. However, the newly-formed osteoid rapidly calcified after withdrawal of bFGF treatment. The data indicate that bFGF not only stimulates bone formation on pre-existing bone surfaces but also induces de novo formation of bone spicules within the marrow cavity, which results in partial restoration of lost cancellous bone mass in osteopenic OVX rats after only 14 days of treatment with the growth factor. These findings suggest that bFGF merits consideration for development as a potential treatment for patients with severe osteopenia who are unresponsive to conventional osteoporosis therapies.     

Dose-response effects of 2-methoxyestradiol on estrogen target tissues in the ovariectomized rat

In three experiments, we evaluated the pharmacological effects of 2-methoxyestradiol (2ME(2)) on several estrogen target tissues. Experiment 1: we gavaged recently ovariectomized (OVX) 9.5-wk-old rats with 2ME(2) at doses of 0, 0.1, 1, 4, 20, and 75 mg/kg in a 21-d dose-response study. 2ME(2) reduced body weight and serum cholesterol, increased uterine weight and epithelial cell height, and inhibited longitudinal and radial bone growth compared with values in the untreated OVX rat. All doses of 2ME(2) maintained cancellous bone mass at the baseline level, the lowest effective dose being 20-fold less than a uterotrophic dose. Experiment 2: in an 8-wk experiment in adult OVX rats, a nonuterotrophic dose of 2ME(2) (4 mg/kg x d) suppressed body weight gain, inhibited bone formation in cancellous bone and partially prevented bone loss in the tibial metaphysis. Experiment 3: in weanling rats, ICI 182,780 did not antagonize the effect of 2ME(2). We conclude that 2ME(2) antagonizes the skeletal changes that follow OVX at doses that have minimal or no effects in the uterus in both young and adult rats; 2ME(2) does not appear to act via estrogen receptors and is active on bone at doses well below those required for tumor suppression in mice. 2ME(2), through a novel pathway, may be a useful alternative to conventional hormone replacement therapy for prevention of postmenopausal bone loss.     

The catechol estrogen, 4-hydroxyestrone, has tissue-specific estrogen actions

Recent data indicate that the catechol estrogen, 2-hydroxyestrone (2-OHE(1)), has no effect on any target tissue including bone, whereas 16 alpha-hydroxyestrone (16 alpha-OHE(1)) exerts tissue-selective estrogen agonist activity. The effect of the catechol estrogen, 4-hydroxyestrone (4-OHE(1)), putatively associated with tumorigenesis, has not been studied in the skeleton. The purpose of this study was to assess the effect of 4-OHE(1) on tibia, uterine and mammary gland histology and blood cholesterol in ovariectomized (OVX'd) growing rats. Ten-week-old female Sprague-Dawley rats were injected subcutaneously with 200 microg/kg BW per day with 4-OHE(1), 17 beta-estradiol (E(2)) or vehicle for three weeks. OVX resulted in uterine atrophy, increased body weight, radial bone growth and cancellous bone turnover, and hypercholesterolemia. E(2) prevented these changes with the expected exception that the subcutaneous infusion of this high dose of estrogen did not prevent the hypercholesterolemia. 4-OHE(1) prevented the increase in blood cholesterol and the increase in body weight. 4-OHE(1) appeared to have partial estrogen activity in the uterus; uterine weight and epithelial cell height were significantly greater than the OVX rats but significantly less (twofold) than the E(2) animals. Analysis of variance indicated that 4-OHE(1) slightly decreased the periosteal mineral apposition rate (P<0.05) compared with vehicle-treated rats but had no effect on double-labeled perimeter or bone formation rate. Similarly, 4-OHE(1) was a partial estrogen agonist on cancellous bone turnover. The data suggest that the catechol estrogen, 4-OHE(1), unlike 2-OHE(1), has estrogen activity. Furthermore, the profile of activity differs from that of 16 alpha-OHE(1). Our results suggest that estrogen metabolites may selectively influence estrogen-target tissues and, concomitantly, modulate estrogen-associated disease risk.     

Direct effects of 17 beta-estradiol on trabecular bone in ovariectomized rats.

High-affinity nuclear binding sites for 17 beta-estradiol (17 beta E2) were recently found in bone cells; however, the mechanism by which estrogen exerts its effect on bone in vivo is still unknown. To study if estrogen acts on bone directly, we used an experimental model in which test substances are infused locally into rat femur trabecular bone. Sprague-Dawley rats weighing 150-160 g were ovariectomized (OVX) and 14 days later a polyethylene tube (1 mm in diameter) connected to an Alzet osmotic minipump was implanted into the distal femur 9 mm from the joint. 17 beta E2 (24 microliters/day at 0.01-1 nM), 17 alpha-estradiol (17 alpha E2) (24 microliters/day at 1 nM), or phosphate-buffered saline (NaCl, 8 g/liter; KCl, 0.2 g/liter; KH2PO4, 0.2 g/liter; Na2HPO4.7H2O, 2.16 g/liter) was infused for 8 days. The contralateral limb remained intact. Animals were sacrificed and bones were examined by histomorphometry. Ovariectomy caused a 50% loss in trabecular bone volume (TBV) in the secondary spongiosa (from 20.3% +/- 1.7% to 9.6% +/- 1.1%; mean +/- SEM), a 2-fold increase in osteoclast number (to 4.0 +/- 0.4 per mm), a 3-fold increase in relative resorption surfaces (to 24.8% +/- 2.9%), a 9-fold increase in osteoblast number (to 11.3 +/- 2.1 per mm), and an 8-fold increase in relative osteoid surface (to 9.6% +/- 1.7%). The local infusion of 17 beta E2 for 8 days into OVX rats (i) restored the TBV dose dependently to 75% and 85% of control (non-OVX) levels, at 0.1 nM and 1 nM 17 beta E2, respectively; (ii) decreased osteoclast number and the relative resorption surface to control (non-OVX) levels; and (iii) further increased osteoblast number and the relative osteoid surface dose dependently (by 5-fold at 1 nM 17 beta E2). Phosphate-buffered saline infusion was without effect. Infusion of 17 alpha E2 had no effect on TBV, osteoclast number, or resorption surface but increased slightly the osteoblast number and the osteoid surface. Its potency was 1/100 that of 17 beta E2. The local infusion of 17 beta E2 or 17 alpha E2 had no effect on body or uterine weight. We conclude from these findings that estrogen delivered directly to the bone of OVX rats in vivo at 2.4 and 24 fmol/day acted locally to inhibit bone resorption and stimulate bone formation.     

Neuropeptide-Y stimulation of luteinizing hormone-releasing hormone secretion from the median eminence in vitro by estrogen-dependent and extracellular Ca2+-independent mechanisms

The roles of estrogen and extracellular calcium (Ca2+) in neuropeptide-Y (NPY)-stimulated LHRH release from median eminence (ME) fragments in vitro were examined. Ovariectomized (OVX) rats received one or several sc implants of Silastic tubes containing estradiol benzoate (235 micrograms/ml sesame oil) or vehicle. Plasma estrogen concentrations were similar to levels during the estrous cycle. These estrogen treatments were equally effective in reducing the elevated plasma levels of LH in vehicle-treated OVX rats. Animals were killed 3 days after implantation, and ME fragments were incubated in medium for 30 min (control), followed by a second 30-min period (test) in medium containing NPY or potassium chloride (K+). Estrogen treatment increased the basal release of LHRH and the ME concentration of LHRH in a dose-related fashion. NPY (0.1-10 microM) increased LHRH secretion in a dose-related manner from ME fragments obtained from estrogen-treated OVX rats, but had no effect on MEs from hormonally untreated OVX rats. Treatment with higher doses of estrogen enhanced the LHRH secretory response of ME fragments to NPY (1-10 microM). K+-stimulated LHRH release from ME fragments from estrogen-treated rats was completely eliminated in Ca2+-free medium containing EGTA. In contrast, LHRH release elicited by NPY (10 microM) was unchanged in Ca2+-free medium in both the absence and presence of cobalt chloride (Co2+). Decreasing the Ca2+ concentration from 2.5 to 0.25 mM reduced K+-stimulated LHRH release 7-fold, while NPY-stimulated LHRH secretion was not affected. These results indicate that NPY stimulation of LHRH release from the ME in vitro is related to prior circulating levels of estrogen, but does not require extracellular Ca2+ in the incubation medium. NPY may enhance LHRH release in an estrogen-dependent manner during the estrous cycle and before the LH surge on proestrous.     

Amylin inhibits ovariectomy-induced bone loss in rats

Amylin (AMY), a peptide co-secreted with insulin by pancreatic beta-cells, inhibits bone resorption and stimulates osteoblastic activity. The ovariectomized (OVX) rat is an established animal model for human osteoporosis. Thus, the present experiment was performed to study the effects of AMY on estrogen deficiency-induced bone loss in rats. Thirty-one 6-month-old Wistar rats were randomized by body weight (BW) into two groups. The first underwent surgical OVX (n=21). The second was sham-operated (SH; n=10). Sixty days after surgery, 11 OVX rats were s.c. injected with rat AMY (3 microg/100 g BW/day, for 30 days; OVX+AMY), and 10 with solvent alone in the same way (0.15 ml/100 g BW; OVX). Each rat, housed in an individual cage, was fed daily the mean quantity of diet consumed the day before by SH rats. This diet contained 0.24% calcium and 0. 16% phosphorus. The 31 animals were killed on day 90. No difference in daily weight gain and BW was observed between groups. Neither AMY treatment nor OVX had any significant effect upon femoral morphology, femoral failure load, diaphyseal femoral density (representative of cortical bone) and total femoral calcium content. Nevertheless, both distal metaphyseal (representative of cancellous bone) and total femoral bone densities were higher in SH and OVX+AMY than in OVX rats. The highest plasma osteocalcin concentration was measured in OVX+AMY rats. Simultaneously, urinary deoxypyridinoline excretion was lower in OVX+AMY than in OVX rats. These results indicate that in OVX rats, AMY treatment inhibited trabecular bone loss both by inhibiting resorption and by stimulating osteoblastic activity.     

氟化钠对去卵巢大鼠胫骨作用的骨形态计量学研究

目的 了解卵巢切作大鼠胫骨对氟化钠的治疗反应。方法 将２４只雌性大鼠随机分成３组,单纯切卵巢组、对照组和氟化钠治疗组。对单纯切卵巢组和氟化钠治疗组大鼠行卵巢切除手术,建立骨质疏松动物模型,氟化钠治疗组于卵巢切除术后１个月予氟化钠,给药３个月后处死。用骨形态计量学方法检测卵巢切除大鼠无后肢胫骨对氟化钠的治疗反应。结果 单纯卵巢切除组大鼠骨小梁体积,平均骨小梁密度较对照组显著较减少（Ｐ〈０．０５）,四     

Effects of chronic prednisolone treatment on bone resorption and bone composition in intact and ovariectomized rats and in ovariectomized rats receiving beta-estradiol

To examine the interactions between estrogen deficiency and glucocorticoid excess on bone metabolism the osteopenic effects of a standard dose of prednisolone (2 mg/kg BW.day) were studied in sham-ovariectomized (Sham-OVX), ovariectomized (OVX), and OVX rats given replacement beta-estradiol (OVX + E2). For 12 weeks six groups of female albino rats aged 4 months which had their skeletons labeled with 45Ca were fed matched amounts of low-calcium (0.1% Ca) hydroxyproline-free diet. The six treatment groups were: group 1, Sham-OVX; group 2, Sham-OVX + prednisolone; group 3, OVX; group 4, OVX + prednisolone; group 5, OVX + E2; group 6, OVX + E2 + prednisolone. Bone resorption was estimated by studying the urinary excretion of hydroxyproline and 45Ca. Parathyroid function was assessed indirectly from urinary cAMP excretion. Treatments did not influence parathyroid activity or serum levels of calcium or 1,25-dihydroxyvitamin D. However, ovariectomy increased bone resorption and induced osteopenia whereas prednisolone decreased bone resorption and formation and caused osteopenia. Ovariectomy increased the rate of bone resorption in prednisolone-treated rats; prednisolone lowered the rates of bone resorption and formation in OVX rats. The osteopenic effects of prednisolone and ovariectomy were additive and independent. E2 protected bone from the osteopenic effects of ovariectomy but did not affect bone loss induced by prednisolone. These results suggest prophylactic estrogen should help to avoid bone loss from estrogen deficiency in patients requiring chronic high dose glucocorticoid treatment.     

Moderately High Consumption of Ethanol Suppresses Bone Resorption in Ovariectomized but not in Sexually Intact Adult Female Rats

Epidemiological studies suggest that moderate consumption of alcoholic beverages may be beneficial for bone in postmenopausal women. To investigate prospectively these uncontrolled obsewations, female rats were divided in four groups of 10 animals each and treated with 1) ovariectomy (OVX) and 2.5% ethanol diet (OVX-ETOH group), 2) OVX and control diet (OVX-C group), 3) sham surgery and 25% ethanol diet (SHAM-ETOH group), or 3) sham surgery and control diet (SHAM-C group). Three weeks after surgery, bone histomor-phometfy revealed that the OVX-C group, as expected, had lower trabecular bone volume and higher parameters of bone formation and resorption than the SHAM-C group (p < 0.01). Intake of ethanol did not change these parameters in the SHAM rats, but in the OVX rats it was associated with sharp reduction in parameters of bone resorption (p < 0.01) without a concomitant effect on parameters of bone formation. The cytokines are believed to contribute to accelerated bone resorption during the early postmenopausal period. Indeed, the peripheral blood monocybc cells (PBMC) from the OVX-C rats produced higher amounts of TNF-α than the PBMC from the SHAM-C rats (p < 0.05) and administration of ethanol prevented this increase in OVX rats but had no effect in SHAM rats. In summary, short-tetm intake of moderate doses of ethanol was associated with markedly different eftects in rats with and without ovarian function. Although ethanol had no significant effect on the bone tissue and TNF-α production of the SHAM rats, it was associated with markedly lower parameters of bone resorption and less TNF-α production in the OVX animals. This suggests that exposure to low-dose ethanol may protect from osteopenia following cessation of ovarian function.     

Selective estrogenic effects of a novel triphenylethylene compound, FC1271a, on bone, cholesterol level, and reproductive tissues in intact and ovariectomized rats

FC1271a is a novel triphenylethylene compound with a tissue-selective profile of estrogen agonistic and weak antagonistic effects. It specifically binds to the estrogen receptor alpha and beta with affinity closely similar to that of toremifene and tamoxifen. To study the in vivo effects of the compound, 4-month-old rats were sham operated (sham) or ovariectomized (OVX) and treated daily for 4 weeks with various doses of FC1271a or vehicle (orally). FC1271a was able to oppose OVX-induced bone loss by maintaining the trabecular bone volume of the distal femur. Accordingly, the OVX-induced loss of bone strength was prevented at doses of 1 and 10 mg/kg. FC1271a also prevented the OVX-induced increase in serum cholesterol in a dose-dependent manner. No significant changes in uterine wet weight or morphology were observed in the OVX-rats treated with 0.1 or 1 mg/kg FC1271a, but at a dose of 10 mg/kg it had a slightly estrogenic effect. In immature rats the effect of FC1271a on uterine wet weight was less stimulatory than that of toremifene or tamoxifen, but more stimulatory than that of raloxifene or droloxifene. The appearance of the dimethylbenzanthracene (DMBA)-induced mammary tumors was inhibited by treatment of DMBA-treated rats with FC1271a in a dose-dependent manner. In human MCF-7 breast cancer cell tumors raised in nude mice in the presence of estrogen, the growth and expression of pS2 marker gene could not be maintained after estrogen withdrawal by treatment with FC1271a. No formation of DNA adducts was observed in the liver of the FC1271a-treated rats. In conclusion, the bone-sparing, antitumor, and cholesterol-lowering effects of FC1271a combined with a low uterotropic activity and lack of liver toxicity indicate that FC1271a could be an important alternative in planning antiosteoporosis therapy for estrogen deficiency.     

Investigation of the effects of progesterone on neuropeptide Y-stimulated luteinizing hormone-releasing hormone secretion from the median eminence of ovariectomized and estrogen-treated rats

We have investigated the hypothesis that administration of progesterone to estrogen-treated ovariectomized (OVX) rats enhances the stimulatory effects of neuropeptide Y (NPY) on the secretion of luteinizing hormone-releasing hormone (LHRH) from median eminence (ME) fragments in vitro. Adult rats were bilaterally OVX and after 2-4 weeks various doses of estrogen were administered subcutaneously in Silastic capsules. Three days later animals were injected subcutaneously with progesterone (1, 2 or 19 mg) or oil vehicle. Three hours later animals were killed, trunk blood collected, and the ME dissected and rinsed in culture medium. Incubation medium was collected after 30 min (control) and synthetic porcine NPY (0.1-10 microM) was applied during the test period. LHRH released into the medium and plasma luteinizing hormone were measured with RIA. NPY significantly stimulated LHRH secretion from MEs obtained from estrogen-treated OVX rats injected with oil vehicle. This stimulation was directly dependent on the degree of estrogen replacement. Administration of physiological doses of progesterone had no effect on NPY-stimulated LHRH release at low physiological levels of estrogen replacement. However, injection of 1 or 2 mg of progesterone into animals receiving the high physiological dose of estrogen slightly, although not significantly, reduced NPY (10 microM)-stimulated LHRH secretion. Treatment with the pharmacological dose of progesterone (19 mg) significantly decreased the ability of NPY to stimulate LHRH release when compared to vehicle-injected controls or to animals receiving 1 mg of progesterone. These results do not support the hypothesis that progesterone enhances NPY-stimulated LHRH secretion.(ABSTRACT TRUNCATED AT 250 WORDS)     

去卵巢大鼠骨髓源性破骨样细胞增殖、分化的改变及雌激素的影响

目的　通过体外骨髓细胞培养诱导破骨样细胞 (osteoclast likecells ,OLC)的形成 ,观察去卵巢对成年大鼠OLC形成及活性的影响以及给予雌激素后的改变。　方法　 3月龄SD大鼠分为对照组、去卵巢组及雌激素替代组。术后 12周处死大鼠 ,取股骨分离骨髓细胞 ,在条件培养液中诱导其向破骨细胞分化。活体观察OLC形成情况并于培养的第 6天行细胞染色 ,以抗酒石酸酸性磷酸酶(TRAP)染色 (+)、细胞核≥ 3个的细胞为OLC ,计数各组OLC及骨陷窝。　结果　 3组中去卵巢组OLC出现早且数量〔(2 7 75± 0 92 )个 /玻片〕明显高于其它两组〔(17 93± 0 6 9)个 /玻片和 (12 81±0 6 1)个 /玻片 ,P <0 0 1〕。雌激素处理能明显抑制OLC的形成 ,但雌激素替代组的OLC仍多于对照组 (P <0 0 5 )。骨陷窝形成的变化与OLC数量改变一致。　结论　本实验结果显示大鼠去卵巢后 ,骨髓干细胞分化形成OLC数量明显增多 ,且活性增强。补充雌激素能够有效抑制OLC形成增加及其活性增强。故雌激素抑制骨吸收的机制至少部分是作用于骨髓干细胞向破骨细胞的分化。     

选择性雌激素受体调节剂雷洛昔芬阻止去卵巢大鼠骨丢失的机制

目的　了解选择性雌激素受体调节剂雷洛昔芬 (RLX)阻止去卵巢大鼠骨丢失的机制。对骨质疏松症模型大鼠进行雌激素及选择性雌激素受体调节剂类药物RLX治疗 ,观察其对去卵巢大鼠骨组织光镜、电镜及骨密度 (BMD)等各种指标的影响。　方法　用 3月龄雌性SD大鼠 32只 ,随机分为卵巢未切除组、卵巢切除组、雌激素治疗组、RLX治疗组 ,5个月后处死 ,检测股骨、腰椎及全身BMD、子宫重量、骨形态。　结果　卵巢切除组经RLX治疗 3个月后腰椎、股骨、全身BMD增加35 %、4 0 %、2 1% ,分别为 (0 2 5 6± 0 0 2 2 ) g/cm2 、(0 2 93± 0 0 15 ) g/cm2 和 (0 36 8± 0 0 2 5 ) g/cm2 ;RLX组大鼠骨小梁表面的破骨细胞数比卵巢切除组减少 ;与卵巢切除组相比 ,雌激素治疗组的子宫重量增加了 5 5 % ,而RLX组则对子宫无明显刺激作用。　结论　RLX及雌激素都具有防治骨质疏松的作用 ,RLX能阻止去卵巢所造成的骨丢失。     

Stimulatory role of substance P on gonadotropin release in ovariectomized rats.

Substance P (SP) has been shown to be present in the hypothalamus and anterior pituitary. To evaluate a possible physiological role of endogenous SP in the control of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) release, specific antiserum against SP (anti-SP) was injected intraventricularly (3 microliters into the third ventricle) or intravenously (50 or 200 microliters) into conscious, ovariectomized (OVX) rats. Third ventricular injection of the antiserum induced a significant decrease in both plasma LH and FSH levels when compared to values in control animals injected with normal rabbit serum (p less than 0.01 and p less than 0.025, respectively). The effect was observed within 10 mi and levels remained suppressed for 60 min. In contrast, intravenous injection of large doses of anti-SP had no effect on the release of both hormones. In order to confirm the stimulatory effect of SP itself, synthetic SP was injected intravenously and intraventricularly into estrogen-primed (E-primed), OVX rats. Synthetic SP dramatically stimulated LH release, but not FSH release when injected either intravenously or intraventricularly at doses of 10 and 50 micrograms (p less than 0.001, p less than 0.005 vs. control, respectively). To investigate any direct action of SP on gonadotropin release from the anterior pituitary gland, synthetic SP was incubated with dispersed anterior pituitary cells harvested from E-primed OVX rats. SP did not affect the release of gonadotropins in vitro. These results indicate that endogenous hypothalamic SP exerts a tonic stimulatory hypothalamic control of basal gonadotropin release in OVX rats.     

Teriparatide [rhPTH (1-34)], but not strontium ranelate, demonstrated bone anabolic efficacy in mature, osteopenic, ovariectomized rats

We compared teriparatide (TPTD) and strontium ranelate (SR) efficacy on bone formation activity in a mature rat model of estrogen-deficiency bone loss. Rats were ovariectomized (OVX) at age 6 months and permitted to lose bone for 2 months to establish osteopenia before initiation of treatment with TPTD (5 or 15 μg/kg · d sc) or SR (150 or 450 mg/kg · d oral gavage). After 3 wk, RT-PCR analyses of bone formation genes in the distal femur metaphysis showed significant elevation of collagen 1α2, osteocalcin, bone sialoprotein, alkaline phosphatase, and Runx2 gene expression at both TPTD doses, relative to OVX controls. SR had no significant effect on expression of these genes. TPTD treatment for 12 wk dose dependently increased lumbar vertebral (LV) and femoral midshaft bone mineral content (BMC) and bone mineral density over pretreatment and age-matched OVX controls. SR 150 increased BMC, and SR 450 increased BMC and bone mineral density of femoral midshaft and LV over OVX controls. There were significant dose-dependent TPTD increases of LV and femoral neck strength, and TPTD 15 also increased midshaft strength compared with pretreatment and age-matched OVX controls. SR did not enhance bone strength relative to pretreatment or age-matched OVX controls. Histomorphometry of the proximal tibial metaphysis showed dose-dependent effects of TPTD on trabecular area, number, width, and osteoblast surface, bone mineralizing surface, and bone formation rate relative to pretreatment and age-matched OVX controls, whereas SR had no effect on these parameters. These findings confirmed the bone anabolic efficacy of teriparatide, but not SR in mature, osteopenic, OVX rats.