Effect of low-dose tacrolimus coadministered with raloxifene on the skeletal system in male rats.

Tacrolimus is an immunosuppressive drug, used to prevent organ transplant rejection. Immunosuppresants are known to unfavorably affect the osseous system. However, in our previous study on bone histomorphometric parameters we observed that low-dose tacrolimus intensified bone formation. The aim of the present study was to investigate the effects of low-dose tacrolimus on bone mechanical properties and mineralization in male rats. The effects of concurrent administration of tacrolimus and raloxifene were also studied. Raloxifene is a selective estrogen receptor modulator, used in the prevention and treatment of postmenopausal osteoporosis. In male rats raloxifene induces moderate intensification of bone mineralization. The experiments were carried out on mature male Wistar rats. The animals were divided into four groups (n = 7): control rats, rats treated with tacrolimus (0.3 mg/kg po), rats treated with raloxifene hydrochloride (5 mg/kg po) and rats treated with tacrolimus and raloxifene hydrochloride concurrently at abovementioned doses. The drugs were administered daily for 4 weeks. Body mass, bone mass and bone mineral content in the tibia, femur and L-4 vertebra, as well as mechanical properties of the whole femur (extrinsic stiffness, ultimate and breaking load, deformation caused by the applied load) and the femoral neck (load at fracture) were examined. Administration of tacrolimus at a dose of 0.3 mg/kg po for 4 weeks did not affect bone mechanical properties and mineralization. Concurrent administration of tacrolimus and raloxifene resulted in changes similar to those caused by raloxifene alone (statistically significant increases in the bone mass/body mass ratio, bone mineral content/body mass ratio and bone mineral content/bone mass ratio in comparison with the control rats, and no effect on bone mechanical properties). Results of the present study do not support the hypothesis that tacrolimus may be useful as a drug stimulating bone formation in skeletal diseases.

Effects of raloxifene on development of the methotrexate-induced changes in bone mechanical properties of male rats.

Methotrexate, a cytostatic and immunosuppressive drug, has been reported to deteriorate the osseous system. Raloxifene, a selective estrogen receptor modulator, is used in the prevention and treatment of postmenopausal osteoporosis. There is a lack of data on possible ways of preventing the unwanted skeletal effects of prolonged immunosuppressive therapy. The aim of the present study was to investigate the effects of raloxifene on mechanical properties of the femur in male rats administered methotrexate. The experiments were carried out on mature male Wistar rats, which were divided into 6 groups: controls, rats administered raloxifene hydrochloride (5 mg/kg p.o.), rats administered methotrexate (0.5 mg/kg p.o. or i.m.), and rats administered raloxifene hydrochloride (5 mg/kg p.o.) plus methotrexate (0.5 mg/kg p.o. or i.m.). Raloxifene was administered for 28 days and methothrexate was administered for the first 10 days of the experiment. After 28 days of drug administration, mechanical parameters of the whole femur were determined: the extrinsic stiffness, the ultimate load and the breaking load, deformation caused by the ultimate and breaking loads, and the load causing fracture of the femoral neck. Additionally, the mass of isolated femurs and their mineral and calcium content were determined. Intragastrically or intramuscularly administered methotrexate impaired the endurance of the tested bones. Administration of raloxifene alone had no significant effects on the mechanical parameters of the femur. Administration of raloxifene resulted in a reduction of the adverse changes in the osseous system induced by methotrexate. Concluding, the experiments demonstrated a protective action of raloxifene against the effects of methotrexate on the osseous system in male rats.

Raloxifene similarly affects the skeletal system of male and ovariectomized female rats.

Raloxifene, a selective estrogen receptor modulator, is used for prevention and treatment of osteoporosis in postmenopausal women. Raloxifene use in male subjects is increasingly considered and a few clinical studies of its effect on bone turnover have already been performed. The aim of the present study was to investigate the effects of raloxifene on the skeletal system of healthy mature male rats. The experiments were performed on mature male Wistar rats, treated daily with raloxifene hydrochloride at a dose of 5 mg/kg po for 4 weeks. Bone mass, mineral content, macrometric and histomorphometric parameters, as well as mechanical properties were examined. For comparison, we also studied the effects of raloxifene on the skeletal system of mature ovariectomized female rats. Raloxifene administration to male rats caused statistically significant increases in the bone mass/body mass ratio, bone mineral content/body mass ratio and bone mineral content/bone mass ratio in comparison with those of the control rats. Bone mechanical properties and most of histomorphometric parameters remained unchanged. Also in ovariectomized female rats, raloxifene administration caused statistically significant increases in the bone mass/body mass ratio, bone mineral content/body mass ratio and bone mineral content/bone mass ratio in comparison with the results obtained in the ovariectomized control rats, to the level of sham-operated control rats. Moreover, raloxifene counteracted the development of changes in histomorphometric parameters caused by ovariectomy in female rats, but did not significantly affect bone mechanical properties. In conclusion, the changes induced by raloxifene in the skeletal system of male rats were similar to those induced by the drug in ovariectomized female rats.

Raloxifene does not affect the changes in bone histomorphometric parameters induced by low dose tacrolimus in male rats.

Raloxifene is a selective estrogen receptor modulator. The drug reduces bone loss and prevents fractures in postmenopausal women. Tacrolimus, an immunosuppressant, is used to prevent organ transplant rejection. The effect of raloxifene and tacrolimus on the osseous bone in men has not been exhaustively determined. To study the effects of raloxifene, tacrolimus as well as concurrent administration of raloxifene and tacrolimus on the osseous tissue in male rats, a preliminary assessment of the drug action on histomorphometric parameters of rat bones was made. The experiments were carried out on mature male Wistar rats. The animals were divided into six groups, 7 animals each: I--control rats; II--rats which were administered raloxifene (5 mg/kg po daily); III-- rats which were administered tacrolimus (0.3 mk/kg po daily); IV - rats which were administered tacrolimus (0.6 mg/kg po daily; V-- rats which were administered raloxifene (5 mg/kg po daily) and tacrolimus (0.3 mg/kg po daily); VI - rats which were administered raloxifene (5 mg/kg po daily) and tacrolimus (0.6 mg/kg po daily). The drugs were administered for 4 weeks. Body mass, macrometric parameters of the tibia, femur and L-4 vertebra, histomorphometric parameters of tibia (transverse growth, width of osteoid, area of the transverse cross section of bone marrow cavity and cortical bone), and the femur (width of trabeculae, width of epiphyseal cartilage) were examined. The action of raloxifene in male rats was demonstrated through increased width of osteoid. An increased traverse growth of bone and osteoid width as well as transverse cross section of the cortical bone and the marrow cavity and increased thickness of trabeculae were observed in male rats receiving tacrolimus at 0.3 mg/kg. The administration of tacrolimus at 0.6 mg/kg resulted in increased traverse growth of bone and increased thickness of osteoid, whereas the thickness of trabeculae remained unaffected. The results obtained in the rats administered concurrently raloxifene and tacrolimus (at 0.3 mg/kg or at 0.6 mg/kg) were similar to those obtained in the group of rats receiving tacrolimus at 0.3 mg/kg. It seems that the most valuable in entire experimental system of the study are the results obtained in the group receiving tacrolimus at 0.3 mg/kg po, which are indicative of intensified bone remodeling processes with dominant the bone formation process.

Effects of catecholamines on blood pressure in the long bone marrow cavity in rats with bisphosphonate-induced osteopetrosis.

Osteopetrosis is a congenital metabolic bone disease characterized by skeletal sclerosis resulting from defective osteoclast-mediated bone resorption. The disease may, inter alia, be caused by the administration of bisphosphonates (e.g. pamidronate) particularly in young humans. The issue of the effect of pamindronate-induced osteopetrosis on the function of blood circulation and autonomic nervous system remains open. In order to clarify this problem, the present study concentrated on the effect of catecholamines on blood pressure in the marrow cavity in rats with pamindronate-induced osteopetrosis. The experiments consisted in pamidronate administration to young male Wistar rats at doses of 3 mg/kg sc, for 3 or 6 weeks. Norepinephrine, epinephrine, isoprenaline as well as adrenoceptor antagonists (phentolamine and propranolol) were administered to the controls and the rats with pamindronate-induced osteopetrosis. The examinations demonstrated that rats with pamidronate-induced osteopetrosis displayed increased blood pressure in the marrow cavity. In addition, a disorder in the effect of catecholamines on blood pressure in the marrow cavity of osteopetrotic bone was observed.

Effects of standard heparin and low-molecular-weight heparins on the formation of murine osteoclasts in vitro.

Long-term administration of heparin can lead to development of osteoporosis. The aim of the present study was to examine the effects of standard heparin and low-molecular-weight heparins (nadroparin, enoxaparin, parnaparin and dalteparin) on osteoclast formation from neonatal murine bone marrow cells stimulated by 1,25-dihydroxyvitamin D3 in vitro. Standard heparin (0.1-10 IU/ml) and low-molecular-weight heparins (1-100 anti-Xa IU/ml) affected the formation of osteoclasts in two directions. In the rat bone marrow cell cultures, at lower concentrations, the heparins tended to increase the formation of osteoclasts, whereas at the highest concentrations (10 IU/ml and 100 anti-Xa IU/ml, respectively) they tended to decrease the number of osteoclasts. In the mouse bone marrow cell culture, the heparins suppressed the formation of osteoclasts, with the exception of standard heparin at 0.1 IU/ml which intensified the process. Results of the present study indicate species differences in the sensitivity of bone marrow cells to standard heparin and low-molecular-weight heparins.

Differential effects of genistein, estradiol and raloxifene on rat osteoclasts in vitro.

Genistein, a major phytoestrogen of soy, is considered a potential drug for prevention and treatment of postmenopausal osteoporosis. It is not clear whether mechanism of action of genistein on bone turnover is distinct from that of estradiol or raloxifene. The aim of the present study was to investigate the effects of genistein on the formation of osteoclasts from neonatal rat bone marrow cells in vitro, and compare them with those of estradiol and raloxifene. Formation of osteoclasts was stimulated by 1,25-dihydroxyvitamin D3, added to the culture media on the second day after plating, together with genistein (10(-8)-10(-5) M), estradiol (10(-10)-10(-7) M) or raloxifene (10(-9)-10(-6) M). The bone marrow cell culture lasted 7 or 9 days. Number of osteoclasts and number of osteoclast "ghosts" (necrotic giant cells) were determined. Genistein, estradiol and raloxifene, at some concentrations, decreased the number of osteoclasts after 9-day culture of bone marrow cells. Genistein decreased the number at 10(-8) M because of decreasing the viability of osteoclasts, whereas at 10(-5) M due to attenuation of osteoclast formation. Estradiol decreased the osteoclast number at 10(-9) M due to decreasing their viability, whereas at 10(-8) and 10(-7) M it was the effect of both decreasing the viability and inhibition of the formation. Decreases in the number of osteoclasts caused by raloxifene (10(-9), 10(-8) M were the effect of decreasing the viability of these cells.

Effect of adminitration of etidronate and retinol on bone mechanical properties in ovariectomized rats.

The experiments were carried out on rats, divided into 7 groups: I-sham-operated control rats, II-ovariectomized (OVX) control rats, II- OVX+etidronate (10 mg/kg po), IV-OVX+retinol (700 IU/kg po), V-OVX+retinol (3,500 IU/kg po), VI-OVX+etidronate (10 mg/kg po)+retinol (700 IU/kg po), VII-OVX+etidronate (10 mg/kg po)+retinol (3 500 IU/kg po). The drugs were administered once a day for 4 weeks. Bone mass, content of mineral substances and calcium were examined in the femur, tibia and L-4 vertebra. In the femur, mechanical properties of the whole bone supported on its epiphyses (the ultimate load, the breaking load and the deformation caused by the applied load) and of the femoral neck (the load causing the fracture) were studied. Bilateral ovariectomy induced unfavorable changes in mechanical properties of rat bones, which were partially prevented by administration of etidronate. Retinol at 3,500 IU/kg po caused intensification of the osteoporotic changes, especially it worsened the mechanical properties of bones. The results of the present study do not indicate the existence of any interaction between retinol and etidronate concerning mechanical properties of bones in OVX rats.

Effects of enoxaparin on histomorphometric parameters of bones in rats.

Enoxaparin sodium is a low-molecular-weight heparin. It is not clear whether the risk of development of osteoporosis after administration of low-molecular-weight heparins is lower than after administration of standard heparin. The aim of the present study was to investigate the effects of enoxaparin on histomorphometric parameters of bones in female Wistar rats (13-15 weeks old at the beginning of the experiment). Enoxaparin was administered at doses of 1000 anti-Xa IU/kg sc daily or 2000 anti-Xa IU/kg sc daily for 4 weeks. Bone mass, mineral and calcium content (in the tibia, femur and L-4 vertebra), length and diameter in the tibia and femur, and histomorphometric parameters of the tibia (periosteal and endosteal transverse growth, width of periosteal and endosteal osteoid, area of the transverse cross-section of the cortical bone in the diaphysis and area of the transverse cross-section of the marrow cavity) and the femur (width of epiphyseal and metaphyseal trabeculae, width of epiphyseal cartilage) were examined. Enoxaparin, administered at doses of 1000 anti-Xa IU/kg sc daily or 2000 anti-Xa IU/kg sc daily for 28 days, induced osteopenic changes in the rat skeletal system. The changes observed in bone histomorphometric parameters indicate that enoxaparin caused the inhibition of bone formation and intensification of bone resorption.

Effects of heparin and low-molecular-weight heparins on bone mechanical properties in rats.

Long-term administration of heparin can be associated with development of osteoporosis. The present study was carried out to compare the effects of standard heparin and two low-molecular-weight heparins (nadroparin and enoxaparin) on bone mechanical properties in rats. The experiment was conducted on 3-month-old female Wistar rats. Standard heparin was administered in doses of 1000 or 2000 IU/kg sc daily, nadroparin and enoxaparin were administered in doses of 1000 or 2000 anti-Xa IU/kg sc daily, for 28 days. Bone mass, length, diameter, mineral content and mechanical properties of the whole femur (extrinsic stiffness, ultimate and breaking load, deformation caused by the applied load) and the femoral neck (load at fracture) were examined. Standard heparin (2000 IU/kg sc daily) weakened the femoral neck. Enoxaparin and the higher doses of standard heparin and nadroparin induced similar unfavourable changes in mechanical properties of the whole femur; the changes were noticeable the most after administration of enoxaparin.

Effect of etoposide on the processes of osseous tissue remodeling in rats.

In the course of tumor metastases into bones, the process of resorption is intensified both as a result of direct influence of tumor cells on normal bone cells, and as a result of bone cell stimulation by cytokines and growth factors, which leads to pathological remodeling of osseous tissue and, in majority of cases, to the development of systemic hypercalcemia. Clinical observations and in vitro research show that also cytostatic drugs may disturb remodeling of bone tissue and cause osteopenia, mostly as a result of their direct effect on osteoblasts. The aim of this study was to investigate in vivo the effect of etoposide on the processes of bone tissue remodeling in rats by assessing macrometric and histomorphometric parameters, as well as mechanical properties of the femur. The tests were carried out on male Wistar rats of initial body mass between 280-310 g, which were divided into three groups (n = 8): I--control group of rats, which were given 0.9% NaCl solution every 7 days (C group), II--rats which were administered etoposide at the dose of 25 mg/kg p.o. every 7 days (E-25 group), III--rats which were given etoposide at one dose of 50 mg/kg i.v. (E-50 group). The experiment lasted 4 weeks. At the end of the experiment, the animals were killed by spinal cord displacement and the following values were determined: the mass, mineral and calcium content in the tested bones, length and diameter of long bones, transverse cross-section surface of tibial cortical bone and marrow cavity, transverse growth of the tibia and width of periosteal and endosteal osteoid in the tibia, as well as the width of osseous trabeculae, the width of epiphysial cartilage and mechanical properties of the femur. The tests showed that etoposide administered every 7 days at the dose of 25 mg/kg p.o. or at one dose of 50 mg/kg i.v. over the period of 28 days, disturbed osseous tissue remodeling processes in rats as a result of impeding the process of bone formation, which led to the impairment of the process of mineralization, weakening mechanical endurance of the femur, and to the development of osteopenia.

Effects of retinol on development of osteopenic changes induced by bilateral ovariectomy in rats.

Skeletal disorders occurring in experimental model of osteopenia caused by bilateral ovariectomy in rats are similar to those observed in postmenopausal women. Retinol is a commonly used vitamin, especially by elderly people. The role of retinol in bone remodeling is not well-established. The aim of the present study was to investigate the effect of retinol administered at doses of 700 IU/kg p.o. daily and 3500 IU/kg p.o. daily for 28 days on the development of osteopenia induced by bilateral ovariectomy in 3-month-old Wistar rats. The experiments were carried out on 4 groups of animals: I (C)--sham-operated control rats, II (OVX)--ovariectomized control rats, III (OVX + R700)--OVX rats treated with retinol (700 IU/kg p.o. daily), IV (OVX + R3500)--OVX rats treated with retinol (3500 IU/kg p.o. daily). Body mass gain, bone mass, mineral and calcium content in the tibia, femur and L-4 vertebra, histomorphometric parameters of the right tibia (width of osteoid, periosteal and endosteal transverse growth, the area of the transverse cross section of the bone marrow and cortical bone) and the right femur (width of epiphyseal and metaphyseal trabeculae, width of epiphyseal cartilage), and mechanical properties of the femur were investigated. Bilateral ovariectomy induced osteopenic skeletal changes in mature female rats. Retinol at doses of 700 IU/kg p.o. daily and 3500 IU/kg p.o. daily decreased bone mass (statistically significantly after treatment with 3500 IU/kg p.o. daily). Retinol at both doses caused statistically significant increases in the width of periosteal osteoid, and, at a dose of 3500 IU/kg p.o. daily, of endosteal osteoid. The increase in the width of osteoid may be the effect of disorder of its mineralization, as the decreases in bone mineral and calcium content were also noted. In mechanical tests of the femur, dose-dependent decreases in the ultimate load, the breaking load and the deformation caused by the applied load were observed after administration of retinol (in comparison with the OVX control rats). Concluding, retinol (especially administered at the dose of 3500 IU/kg daily) intensified the changes in the osseous system caused by estrogen deficiency in rats.

Effects of nadroparin on bone histomorphometric parameters in rats.

Nadroparin calcium is a low-molecular-weight heparin. Low-molecular-weight heparins have a number of advantages over standard heparin (heparin), but it is not clear if low-molecular-weight heparins have less effect on bones than heparin. Administration of heparin can lead to osteoporosis. The aim of the present study was to investigate the effects of nadroparin on the rat osseous system and compare them with those of heparin. The experiments were carried out on female Wistar rats (13-15 weeks old at the beginning of the experiment), divided into 5 groups: I. Control, II. Nadroparin (1000 anti-Xa IU/kg s.c. daily), III. Nadroparin (2000 anti-Xa IU/kg s.c. daily), IV. Heparin (1000 IU/kg s.c. daily), V. Heparin (2000 IU/kg s.c. daily). Nadroparin and heparin were administered for 4 weeks. Bone mass, mineral and calcium content, macrometric and histomorphometric parameters (endosteal and periosteal transverse growth, width of endosteal and periosteal osteoid, transverse cross-section area of the cortical bone in the diaphysis and of the marrow cavity in the tibia, width of epiphyseal cartilage, width of trabeculae in the epiphysis and metaphysis in the femur) were examined. The effect of heparin on the ratio of bone mineral content to bone mass was more pronounced than that of nadroparin. Nadroparin caused unfavorable changes in the investigated bone histomorphometric parameters, similar to those caused by heparin. Nadroparin and heparin caused disorder of bone formation and intensification of bone resorption in rats.

Changes and their regression in the osseous system in rats after administering a cytostatic drug inhibiting tumor cell division in the phase of DNA synthesis.

Chemotherapeutic drugs may disturb the bone tissue metabolism and cause osteopenia, however, the pathomechanism of the damaging effect of cytostatics on this tissue has not been well recognized so far. The detrimental effect may result from a direct cytotoxic action of these drugs on cells remodeling the bone, or on osteogenic cells present in the bone and in the bone marrow, or may be the result of hormonal disorder caused by impaired function of gonads. The aim of this study was to investigate the in vivo effect of 5-fluorouracil (5-FU), a cytostatic agent which inhibits tumor cell division in the phase of DNA synthesis, on the bone remodeling in rats and to examine whether the period of 4 weeks was sufficient for regression of changes elicited by administering 5-FU. Changes in the bone tissue following administration of 5-FU and their regression were evaluated by assessing macrometric and histomorphometric parameters as well as of mechanical properties of the femur. The tests were carried out on male Wistar rats. 5-FU was administered at the doses: 30 mg/kg per os (po) daily for 5 days every 2 weeks; 15 mg/kg im daily for 5 days every 2 weeks; 65 mg/kg im once weekly. Changes in the osseous tissue were examined 4 weeks after the first dose of 5-FU administration. Regression of the changes was examined 8 weeks after the first dose of 5-FU administration (the 5-FU was not administered between 30th and 57th day after the first dose of 5-FU administration). As a result of our research, it was established that 5-FU disturbed the bone remodeling processes in rats, mostly by impairing the process of new bone matrix synthesis, which leads to impaired mineralization process and decreased mechanical endurance of the femur. It was also established that the period of 4 weeks was not sufficient for regression of the changes in the osseous tissue caused by 5-FU administration.

Effect of administration of alendronate sodium and retinol on the mechanical properties of the femur in ovariectomized rats.

Alendronate sodium, an aminobisphosphonate with potent antiresorptive activity, is used in the treatment of postmenopausal osteoporosis. Retinol, as a component of multivitamin preparations, is frequently used especially by elderly people. There are no reports on the interaction of alendronate sodium and retinol. The aim of the present study was to investigate the effect of administration of alendronate sodium and retinol on mechanical properties of the femoral bone in bilaterally ovariectomized rats. The experiments were carried out on 3-month-old Wistar rats, divided into 7 groups: I - sham-operated control rats, II - ovariectomized control rats, III - ovariectomy + alendronate sodium 3 mg/kg po, IV - ovariectomy + retinol 700 IU/kg po, V - ovariectomy + retinol 3500 IU/kg po, VI - ovariectomy + alendronate sodium 3 mg/kg po + retinol 700 IU/kg po, VII - ovariectomy + alendronate sodium 3 mg/kg po + retinol 3500 IU/kg po. The drugs were administered to the rats daily by oral gavage for 28 days. Body mass gain, bone mass, bone mineral content and calcium content in the femur and L-4 vertebra and mechanical properties of the whole femur (extrinsic stiffness, ultimate load, breaking load, deformation caused by the ultimate load) and the neck of the femur (load at fracture), were examined. Bilateral ovariectomy induced osteopenic changes in the rat skeletal system. Alendronate sodium (3 mg/kg po) counteracted the development of osteopenia induced by ovariectomy. Retinol at both used doses unfavorably affected the examined bone parameters of ovariectomized rats. Retinol administered with alendronate sodium lessened the preventive action of alendronate on the development of osteopenic changes in the skeletal system of ovariectomized rats.

[Effect of cyclophosphamide on bone remodeling in rats]. / Wplyw cyklofosfamidu na procesy przebudowy kosci u szczurów.

Neoplasms, with or without metastases in bones, can induce pathological bone remodeling, leading to systemic bone resorption and hypercalcemia or osteomalacia and normocalcemia. The aim of the present study was to investigate the effect of a cytostatic--cyclophosphamide on the skeletal system in rats. The experiments were carried out in male Wistar rats with initial body weight of 212-229 g, divided into 3 groups (n = 6): I--Control, II--Cyclophosphamide (10 mg/kg m.c. i.m. daily for 14 days, and after a 7-day break, for 7 days), III--Cyclophosphamide (20 mg/kg m.c.p.o. daily for the initial 14 days). After 30 days of the experiment, the animals were killed and bone mass, length and diameter of long bones, mineral content in bones, transverse cross-section surfaces of the cortical diaphysis and of the marrow cavity, transverse growth, width of endosteal and periosteal osteoid in the tibia, width of trabeculae, width of epiphyseal cartilage and mechanical features of the femur were examined. Cyclophosphamide caused disorders of bone tissue remodeling. Decreases in bone mass, length, diameter, mineral content in bones, width of trabeculae in the femur, transverse growth, width of osteoid, transverse cross-section surface of the cortical diaphysis, and worsening of mechanical properties of the femur were observed.

Effects of doxycycline on development of changes in histomorphometric parameters of bones induced by bilateral ovariectomy in rats.

Tetracyclines are considered potential medication for the treatment of osteoporosis. The aim of the present study was to investigate the effects of doxycycline on development of unfavorable changes in bone histomorphometric parameters induced by bilateral ovariectomy in rats. Doxycycline at a dose of 20 mg/kg po daily was administered for 28 days to bilaterally ovariectomized and sham-operated 3-month-old Wistar rats. Bone histomorphometric parameters of the tibia (transverse growth, width of periosteal and endosteal osteoid, area of the transverse cross-section of the diaphysis and area of the transverse cross-section of the marrow cavity) and the femur (width of epiphyseal and metaphyseal trabeculae, width of epiphyseal cartilage) were examined. Bilateral ovariectomy caused symptoms of osteopenia in the rat bones. Doxycycline counteracted the unfavorable changes in bone structure caused by estrogen deficiency. However, in the sham-operated rats doxycycline itself induced deleterious effects in the trabecular bone.

[Effects of formestane on the skeletal system in ovariectomized and control rates]. / Wplyw formestanu na uklad kostny u owariektomizowanych i kontrolnych szczurów.

Formestane is an inhibitor of the aromatase enzyme which is uniquely responsible for the generation of estrone and estradiol from androgenic precursors. Formestane is used in the treatment of breast cancer in postmenopausal women. Formestane causes reduction of the estrogen biosynthesis in all tissues where it occurs. Deficiency of estrogens disrypts remodeling of bone tissue. The effect of formestane on bones in not known. The aim of the present study was to investigate the effects of formestane (20 mg/kg s.c. once a week) administered for 4 weeks on the osseous system in bilaterally ovariectomized and non-ovariectomized rats. The experiments were carried out on 4 groups of 3-month-old female Wistar rats:I--Control (non-ovariectomized rats), II--Ovariectomized rats, III--Non-ovariectomized rats + Formestane, IV--Ovariectomized rats + Formestane. In all the groups examined were body weight gain, bone mass, length and diameter, mineral and calcium contents in the tibia and femur, endosteal and periosteal transverse growth, endosteal and periosteal osteoid width transverse cross-section area of the cortical diaphysis and that of the marrow cavity in the tibia, epiphyseal cartilage width, trabeculae width in the epiphysis and metaphysis of the femur. Mechanical properties of the femur were also studied. Bilateral ovariectomy induced osteopenic skeletal changes in female rats. Formestane did not significantly change bone remodeling in non-ovariectomized rats (group III). Formestane administered to the bilaterally ovariectomized rats (group IV) slightly reduced the changes by ovariectomy in the osseus system.

Effects of simvastatin on the development of osteopenia caused by ovariectomy in rats.

Simvastatin is a competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the rate-determining enzyme for cholesterol synthesis which is used in the treatment of hypercholesterolemias, particularly in type IIa and IIb hyperlipoproteinemias, frequently in postmenopausal women. Inhibition of cholesterol synthesis by simvastatin may cause disorders of bone remodelling. The aim of the present study was to investigate the effects of simvastatin (3 mg and 6 mg/kg/day per os) administered for 4 weeks on the development of ovariectomy-induced osteopenia in 3-month-old female Wistar rats. The experiments were carried out on six groups of animals: I (C)--sham operated rats, II (S-3)--sham operated rats + simvastatin 3 mg/kg/day p.o., III (S-6)--sham operated rats + simvastatin 6 mg/kg/day p.o., IV (OVX)--ovariectomized rats, V (OVX + S-3)--ovariectomized rats + simvastatin 3 mg/kg/day p.o., VI (OVX + S-6)--ovariectomized rats + simvastatin 6 mg/kg/day p.o. In all the groups, we examined body weight gain, and macrometrical, histomorphometrical and mechanical parameters. Bilateral ovariectomy induced osteopenic skeletal changes in mature female rats. In cortical bone, ovariectomy intensified resorption processes at the marrow cavity, as indicated by a decrease in endosteal transverse growth and an increase in transverse cross-section surface area of the marrow cavity in the tibia. Intensification of resorption processes was observed in cancellous bone (a statistically significant decrease in the width of trabeculae in the epiphysis and metaphysis of the femur). Structural changes in the long bones resulting from bilateral ovariectomy were manifested by deterioration of mechanical properties of the shaft and neck of the femur. The force needed to fracture the neck and shaft of the femur was significantly smaller than that in sham operated rats. Simvastatin (3 and 6 mg/kg/day p.o.) slightly influenced bone remodelling in sham operated rats. Simvastatin (3 and 6 mg/kg p.o. daily) administered to ovariectomized rats intensified bone formation processes and decreased bone resorption processes induced by bilateral ovariectomy, showing stronger activity at 6 mg/kg.