- Email: [email protected]
Temporal development of muscle atrophy and bone loss induced by Botox in growing rats
S406
Abstracts / Bone 44 (2009) S339–S450
Conclusions: By using OsteoRisk, US measurements were useful to differentiate high and moderate risk patients from low risk patients, although no difference between high and moderate risk patients was observed. OsteoRisk and US of the calcaneous can be used to predict osteoporosis in post-menopausal Brazilian women. Conflict of interest: None declared. doi:10.1016/j.bone.2009.03.313
P402 Association between serum insulin and bone mass in overweight/obese postmenopausal women J. Ilich-Ernsta,*, H. Shinb, P. Liub, O. Kellyb a Nutrition, Food and Exercise Sciences, Tallahassee, USA b Florida State University, Tallahassee, USA It is well established that both fat and muscle masses are positively related to bone mass. Other than just providing a mechanical stimulus, the influence of fat/muscle might be related to their ability to modulate bone cells via other hormonal influences. Higher than necessary food consumption (eventually leading to higher weight/fat) results in continuous higher insulin response. It has been shown in clinical and animal studies that circulating insulin is positively related to BMD/BMC and although individuals with insulin resistance develop other abnormalities, their bone mass is typically higher. This is attributed to the role of insulin in mediating other hormones, including calcitonin, PTH and androgens. Our objective was to evaluate the relationship between insulin and BMD/BMC of various skeletal sites with regard to the adipocity level (expressed as body mass index-BMI kg/m2) in overweight/obese postmenopausal women. Participants included 110 Caucasian healthy women aged (mean ± SD) 55.9 ± 4.1 yr and BMI of 31.9 ± 4.8 kg/m2, without diabetes, insulin resistance, or other diseases/medications known to affect bone. Weight/height was measured in indoor clothing and used to calculate BMI; BMD/BMC was measured by iDXA; fasting serum insulin was measured by ELISA (Alpco Diagnostics, Salem, NH). Women were stratified into 4 categories based on their BMI: overweight (BMI = 25–29.9) obese I (BMI = 30– 34.9), obese II (BMI = 35–39.9), and obese III (BMI > 40). ANOVA results showed significantly higher (p < 0.05) insulin levels in heavier women (6.3 ± 4.0; 9.7 ± 8.1; 12.4 ± 7.5; and 16.0 ± 18.9 μIU/ml, respectively, based on the above stratification). The heavier women also had a higher BMD/BMC in various skeletal sites, although statistical significance was not always reached. Regression models adjusted for BMI and age, showed positive significant (p < 0.05) relationship between BMD/BMC of hip, forearm and spine and insulin levels. Our results show that circulating insulin is positively associated with BMD/BMC of various skeletal sites independently of adiposity/BMI in healthy overweight women. Funded: USDA/CSREES/NRI #2004-05287. Conflict of interest: None declared. doi:10.1016/j.bone.2009.03.314
P403 Calcium intake among different college-student populations C.C. Douglasa, I. Cecicb, V. Shullc, I. Colic-Baricb, M. Piasekd, J.Z. Ilicha,* a Nutrition, Food and Exercise Sciences, Florida State University, Tallahassee, USA b Food Technology and Biotechnology, University of Zagreb, Zagreb, Croatia c Food and Animal Sciences, Alabama A & M, Normal, USA d Medical Research and Occupational Health, University of Zagreb, Zagreb, Croatia
Previous surveys were consistently showing that females fall short of the recommended level for calcium (Ca) consumption. This was particularly true for female college students. The aims of this study were to compare dietary calcium (Ca) intake and its sources, as well as multivitamin/mineral supplement use between African American and Caucasian American female students with a nutrition/health background and African American and Croatian female general student-populations. Additionally, we examined the relationship between Ca intake and weight/BMI within each population. 314 participants aged 18–37 yr completed a validated food frequency questionnaire, assessing their usual Ca intake and supplements. Volunteers included 57 African Americans and 54 Caucasian Americans recruited from Nutrition and/or other Health Sciences departments (NHS), and 100 African American and 103 Croatian women representing the general student population (GSP). Race, height and weight were self-reported. 63% of the African American and 57% of the Caucasian American NHS participants met or exceeded the recommended Ca intake (Dietary Reference Intake, 1000 mg/day), while only 24% of the African American and 30% of the Croatian GSP participants met or exceeded this Ca requirement. The NHS participants were consuming significantly more Ca from milk, cheese, and yogurt (P < 0.05) than the GSP students and were regularly taking multivitamin/mineral supplements. There was an inverse significant relationship between Ca intake and weight/BMI in the African American GSP students only. In conclusion, African American and Caucasian NHS populations consumed significantly more Ca, specifically as dairy Ca, and were more likely to take supplements than either GSP group, suggesting that nutrition/ health education can negate various other influences known to affect Ca intake. Funded in part by USDA/NRI. Conflict of interest: None declared. doi:10.1016/j.bone.2009.03.315
P404 Temporal development of muscle atrophy and bone loss induced by Botox in growing rats J.S. Thomsen*, L.L. Christensen, A. Brüel Institute of Anatomy, University of Aarhus, Aarhus, Denmark Background: Immobilization causes very rapid loss of bone density, and simple bed rest of patients with a herniated disk has thus shown loss of spinal bone density of 1–2% per week. Botulinum toxin (Botox) is a neuro-muscular blocking agent, which inhibits the release of acetylcholine from the motor endplates. Muscular injections with Botox paralyze the muscles and cause temporary immobilization of the injected limb. The aim of the study was to investigate the temporal development of muscle atrophy and bone loss in rats with one hind limb immobilized with Botox. Methods: 108 three-months-old female Wistar rats were randomized into 9 groups with 12 animals in each group. One group was killed at the initiation of the study and served as baseline. At baseline, the rats in four groups (BTX) were injected with a total 2 IU Botox distributed in the quadriceps (1 IU), hamstrings (1/2 IU), and posterior calf muscles (1/2 IU) of the right hind limb. The rats in the remaining four groups (Ctrl) were injected with saline. A BTX and a Ctrl group were killed after 1 week, 2 weeks, 3 weeks, and 4 weeks. The left and right hind limbs were carefully dissected free in a standardized manner and weighed. The rectus femoris muscle was isolated, weighed, and cut into halves and the cross sectional area (CSA) was determined from high resolution digital images of the cut surface. The left and right femora were carefully dissected free and whole bone BMD determined by pDEXA.
Abstracts / Bone 44 (2009) S339–S450
Results: The right hind limb weight was significantly reduced by 15%, 28%, 36%, 41% (right vs left) and by 22%, 43%, 52%, 54% (BTX vs baseline) after 1, 2, 3, and 4 weeks, respectively. The right rectus femoris weight was significantly reduced by 23%, 47%, 58%, 61% (right vs left) and by 28%, 54%, 64%, 67% (BTX vs baseline) and the right rectus femoris CSA was significantly reduced by 33%, 40%, 53%, 51% (right vs left) and by 19%, 46%, 56%, 56% (BTX vs baseline) after 1, 2, 3, and 4 weeks, respectively. The right femoral BMD was significantly reduced by 2.4%, 3.6%, 5.5%, 7.9% (right vs left) and non-significantly reduced by −1.9%, 1.2%, 3.7% and significantly reduced by 6.2% (BTX vs baseline) after 1, 2, 3, and 4 weeks, respectively. Conclusion: Botox induced a rapid and time-dependent loss of muscle and bone mass. The loss of BMD was delayed compared with the loss of muscle mass. The Botox model is fast and straightforward and is well suited for studying bone and muscle loss induced by immobilization. Conflict of interest: None declared. doi:10.1016/j.bone.2009.03.316
P405 Bone mass in women with subclinical hypothyroidism on levothyroxine replacement therapy J.M. Lavado-Garcíaa,*, M.L. Canal-Macíasb, J.F. Calderón-Garcíab, R. Roncero-Martínc, M.C. Costa-Fernándezb, J.D. Pedrera-Zamoranob a Department of Medicine I, Universidad de Extremadura, Cáceres, Spain b Department of Nursing, Universidad de Extremadura, Cáceres, Spain c Department of Nursing, Universidad de Extremadura, Badajoz, Spain Background and aim: The results of studies examining the influence of subclinical hypothyroidism on bone mass have generated considerable interest but also some controversy. The present research aims to evaluate, in different skeletal sites, the effect of levothyroxine replacement therapy on bone mineral density in women. Methods: A group of 262 biochemically and clinically euthyroid women (mean age 55.22 ± 9.73 years old) with subclinical hypothyroidism on levothyroxine replacement therapy for at least six months was compared to 262 controls pair-matched for sex and age. Levothyroxine mean doses were 86.89 ± 37.34 μg/day. Bone mass measurements were assessed using peripheral quantitative computed tomography (pQCT) of the non-dominant distal radius, phalangeal quantitative bone ultrasound (QUS) and dual energy Xray absorptiometry (DXA) in lumbar spine and hip. Results: No differences were observed between patients and control in bone mass measurements (QUS, pQCT and DEXA) and weight, height, body mass index (BMI), menopausal status, age of menarche and years since menopause. Simple linear regression analyses between bone measurements and doses of levothyroxine only showed significant positive relations with total (p = 0.0259) and cortical + subcortical (p = 0.0372) bone density by pQCT. Conclusion: In women biochemically and clinically euthyroid with subclinical hypothyroidism, levothyroxine replacement therapy was accompanied by normal bone mass values. Conflict of interest: None declared. doi:10.1016/j.bone.2009.03.317
P406 Effects of selective serotonin reuptake inhibitors on bone mechanical properties in ovariectomized and non-ovariectomized rats J. Folwarczna*, M. Pytlik, B. Nowinska, U. Cegiela, P. Molin, T. Hanke, H.I. Trzeciak Department of Pharmacology, Medical University of Silesia, Sosnowiec, Poland
S407
Administration of selective serotonin reuptake inhibitors (SSRIs), drugs used in the treatment of depression, may be associated with the increased risk of fracture. SSRIs are often prescribed to postmenopausal women. There are a few experimental studies on fluoxetine skeletal effects. To our knowledge, the effects of other SSRIs on bones have not been studied in experimental conditions. The aim of the present study was to investigate how SSRIs (fluoxetine and fluvoxamine) affect the skeletal system of female rats and whether their possible effects depend on estrogen status. The experiments were carried out on 15–17-week-old Wistar rats. The effects of fluoxetine hydrochloride (10 mg/kg p.o.) and fluvoxamine maleate (30 mg/kg p.o.) on bones of normal nonovariectomized rats, bilaterally ovariectomized (OVX, estrogendeficient) rats and OVX rats supplemented with estradiol (0.2 mg/ kg p.o.), in comparison with appropriate control groups, were studied (n = 8–10 per group). The ovariectomy was performed 7–9 days before the start of a four-week period of daily administration of the drugs. Bone geometric parameters, mass, mass of bone mineral in the tibia, femur and L-4 vertebra, as well as mechanical properties of tibial metaphysis and femoral diaphysis in three-point bending tests and femoral neck in a compression test were assessed (Instron 3342 500N apparatus). In OVX control rats, the ratio of bone mineral mass to bone mass was decreased and mechanical properties of tibial metaphysis and femoral neck were worsened in comparison with sham-operated control rats. Supplementation with estradiol improved bone mineralization, but did not improve mechanical properties of bones in OVX rats. Fluoxetine worsened mechanical properties of the tibial metaphysis both in OVX and non-ovariectomized rats; moreover, it decreased bone mass and mass of bone mineral (not affecting the bone mineral/bone mass ratio) in OVX rats. Fluoxetine did not significantly affect mechanical properties of the femoral neck and diaphysis. Fluvoxamine did not affect bone mass, mineralization and mechanical properties in female rats. Concluding, effects of the investigated SSRIs on rat bone mechanical properties do not depend on estrogen status. Results of the present study also indicate that the skeletal effects of different SSRIs should be considered separately. Acknowledgments: This study was supported by grant No N401 059 32/1412 from the Ministry of Science and Higher Education, Poland. Conflict of interest: None declared. doi:10.1016/j.bone.2009.03.318
P407 Serotonin effects on the skeletal system may depend on estrogen status: Differential effects on bone mechanical properties in non-ovariectomized and ovariectomized rats J. Folwarczna*, T. Hanke, P. Molin, H.I. Trzeciak Department of Pharmacology, Medical University of Silesia, Sosnowiec, Poland Serotonin has been recently reported to be involved in regulation of bone metabolism in vitro and in vivo. Estradiol has been shown to interact with serotonergic system. The aim of the present study was to investigate how elevated peripheral levels of serotonin or inhibition of serotonin synthesis by p-chlorophenylalanine affects the skeletal system of female rats and whether the serotonin effects on bones depend on estrogen status. The experiments were carried out on 15–17-week-old Wistar rats. The effects of serotonin (serotonin creatinine sulfate complex, 10 mg/ kg/day, s.c.) and p-chlorophenylalanine (a tryptophan hydroxylase inhibitor, 100 mg/kg/day, i.p.) on bones of normal non-ovariecto-
Abstracts / Bone 44 (2009) S339–S450
Conclusions: By using OsteoRisk, US measurements were useful to differentiate high and moderate risk patients from low risk patients, although no difference between high and moderate risk patients was observed. OsteoRisk and US of the calcaneous can be used to predict osteoporosis in post-menopausal Brazilian women. Conflict of interest: None declared. doi:10.1016/j.bone.2009.03.313
P402 Association between serum insulin and bone mass in overweight/obese postmenopausal women J. Ilich-Ernsta,*, H. Shinb, P. Liub, O. Kellyb a Nutrition, Food and Exercise Sciences, Tallahassee, USA b Florida State University, Tallahassee, USA It is well established that both fat and muscle masses are positively related to bone mass. Other than just providing a mechanical stimulus, the influence of fat/muscle might be related to their ability to modulate bone cells via other hormonal influences. Higher than necessary food consumption (eventually leading to higher weight/fat) results in continuous higher insulin response. It has been shown in clinical and animal studies that circulating insulin is positively related to BMD/BMC and although individuals with insulin resistance develop other abnormalities, their bone mass is typically higher. This is attributed to the role of insulin in mediating other hormones, including calcitonin, PTH and androgens. Our objective was to evaluate the relationship between insulin and BMD/BMC of various skeletal sites with regard to the adipocity level (expressed as body mass index-BMI kg/m2) in overweight/obese postmenopausal women. Participants included 110 Caucasian healthy women aged (mean ± SD) 55.9 ± 4.1 yr and BMI of 31.9 ± 4.8 kg/m2, without diabetes, insulin resistance, or other diseases/medications known to affect bone. Weight/height was measured in indoor clothing and used to calculate BMI; BMD/BMC was measured by iDXA; fasting serum insulin was measured by ELISA (Alpco Diagnostics, Salem, NH). Women were stratified into 4 categories based on their BMI: overweight (BMI = 25–29.9) obese I (BMI = 30– 34.9), obese II (BMI = 35–39.9), and obese III (BMI > 40). ANOVA results showed significantly higher (p < 0.05) insulin levels in heavier women (6.3 ± 4.0; 9.7 ± 8.1; 12.4 ± 7.5; and 16.0 ± 18.9 μIU/ml, respectively, based on the above stratification). The heavier women also had a higher BMD/BMC in various skeletal sites, although statistical significance was not always reached. Regression models adjusted for BMI and age, showed positive significant (p < 0.05) relationship between BMD/BMC of hip, forearm and spine and insulin levels. Our results show that circulating insulin is positively associated with BMD/BMC of various skeletal sites independently of adiposity/BMI in healthy overweight women. Funded: USDA/CSREES/NRI #2004-05287. Conflict of interest: None declared. doi:10.1016/j.bone.2009.03.314
P403 Calcium intake among different college-student populations C.C. Douglasa, I. Cecicb, V. Shullc, I. Colic-Baricb, M. Piasekd, J.Z. Ilicha,* a Nutrition, Food and Exercise Sciences, Florida State University, Tallahassee, USA b Food Technology and Biotechnology, University of Zagreb, Zagreb, Croatia c Food and Animal Sciences, Alabama A & M, Normal, USA d Medical Research and Occupational Health, University of Zagreb, Zagreb, Croatia
Previous surveys were consistently showing that females fall short of the recommended level for calcium (Ca) consumption. This was particularly true for female college students. The aims of this study were to compare dietary calcium (Ca) intake and its sources, as well as multivitamin/mineral supplement use between African American and Caucasian American female students with a nutrition/health background and African American and Croatian female general student-populations. Additionally, we examined the relationship between Ca intake and weight/BMI within each population. 314 participants aged 18–37 yr completed a validated food frequency questionnaire, assessing their usual Ca intake and supplements. Volunteers included 57 African Americans and 54 Caucasian Americans recruited from Nutrition and/or other Health Sciences departments (NHS), and 100 African American and 103 Croatian women representing the general student population (GSP). Race, height and weight were self-reported. 63% of the African American and 57% of the Caucasian American NHS participants met or exceeded the recommended Ca intake (Dietary Reference Intake, 1000 mg/day), while only 24% of the African American and 30% of the Croatian GSP participants met or exceeded this Ca requirement. The NHS participants were consuming significantly more Ca from milk, cheese, and yogurt (P < 0.05) than the GSP students and were regularly taking multivitamin/mineral supplements. There was an inverse significant relationship between Ca intake and weight/BMI in the African American GSP students only. In conclusion, African American and Caucasian NHS populations consumed significantly more Ca, specifically as dairy Ca, and were more likely to take supplements than either GSP group, suggesting that nutrition/ health education can negate various other influences known to affect Ca intake. Funded in part by USDA/NRI. Conflict of interest: None declared. doi:10.1016/j.bone.2009.03.315
P404 Temporal development of muscle atrophy and bone loss induced by Botox in growing rats J.S. Thomsen*, L.L. Christensen, A. Brüel Institute of Anatomy, University of Aarhus, Aarhus, Denmark Background: Immobilization causes very rapid loss of bone density, and simple bed rest of patients with a herniated disk has thus shown loss of spinal bone density of 1–2% per week. Botulinum toxin (Botox) is a neuro-muscular blocking agent, which inhibits the release of acetylcholine from the motor endplates. Muscular injections with Botox paralyze the muscles and cause temporary immobilization of the injected limb. The aim of the study was to investigate the temporal development of muscle atrophy and bone loss in rats with one hind limb immobilized with Botox. Methods: 108 three-months-old female Wistar rats were randomized into 9 groups with 12 animals in each group. One group was killed at the initiation of the study and served as baseline. At baseline, the rats in four groups (BTX) were injected with a total 2 IU Botox distributed in the quadriceps (1 IU), hamstrings (1/2 IU), and posterior calf muscles (1/2 IU) of the right hind limb. The rats in the remaining four groups (Ctrl) were injected with saline. A BTX and a Ctrl group were killed after 1 week, 2 weeks, 3 weeks, and 4 weeks. The left and right hind limbs were carefully dissected free in a standardized manner and weighed. The rectus femoris muscle was isolated, weighed, and cut into halves and the cross sectional area (CSA) was determined from high resolution digital images of the cut surface. The left and right femora were carefully dissected free and whole bone BMD determined by pDEXA.
Abstracts / Bone 44 (2009) S339–S450
Results: The right hind limb weight was significantly reduced by 15%, 28%, 36%, 41% (right vs left) and by 22%, 43%, 52%, 54% (BTX vs baseline) after 1, 2, 3, and 4 weeks, respectively. The right rectus femoris weight was significantly reduced by 23%, 47%, 58%, 61% (right vs left) and by 28%, 54%, 64%, 67% (BTX vs baseline) and the right rectus femoris CSA was significantly reduced by 33%, 40%, 53%, 51% (right vs left) and by 19%, 46%, 56%, 56% (BTX vs baseline) after 1, 2, 3, and 4 weeks, respectively. The right femoral BMD was significantly reduced by 2.4%, 3.6%, 5.5%, 7.9% (right vs left) and non-significantly reduced by −1.9%, 1.2%, 3.7% and significantly reduced by 6.2% (BTX vs baseline) after 1, 2, 3, and 4 weeks, respectively. Conclusion: Botox induced a rapid and time-dependent loss of muscle and bone mass. The loss of BMD was delayed compared with the loss of muscle mass. The Botox model is fast and straightforward and is well suited for studying bone and muscle loss induced by immobilization. Conflict of interest: None declared. doi:10.1016/j.bone.2009.03.316
P405 Bone mass in women with subclinical hypothyroidism on levothyroxine replacement therapy J.M. Lavado-Garcíaa,*, M.L. Canal-Macíasb, J.F. Calderón-Garcíab, R. Roncero-Martínc, M.C. Costa-Fernándezb, J.D. Pedrera-Zamoranob a Department of Medicine I, Universidad de Extremadura, Cáceres, Spain b Department of Nursing, Universidad de Extremadura, Cáceres, Spain c Department of Nursing, Universidad de Extremadura, Badajoz, Spain Background and aim: The results of studies examining the influence of subclinical hypothyroidism on bone mass have generated considerable interest but also some controversy. The present research aims to evaluate, in different skeletal sites, the effect of levothyroxine replacement therapy on bone mineral density in women. Methods: A group of 262 biochemically and clinically euthyroid women (mean age 55.22 ± 9.73 years old) with subclinical hypothyroidism on levothyroxine replacement therapy for at least six months was compared to 262 controls pair-matched for sex and age. Levothyroxine mean doses were 86.89 ± 37.34 μg/day. Bone mass measurements were assessed using peripheral quantitative computed tomography (pQCT) of the non-dominant distal radius, phalangeal quantitative bone ultrasound (QUS) and dual energy Xray absorptiometry (DXA) in lumbar spine and hip. Results: No differences were observed between patients and control in bone mass measurements (QUS, pQCT and DEXA) and weight, height, body mass index (BMI), menopausal status, age of menarche and years since menopause. Simple linear regression analyses between bone measurements and doses of levothyroxine only showed significant positive relations with total (p = 0.0259) and cortical + subcortical (p = 0.0372) bone density by pQCT. Conclusion: In women biochemically and clinically euthyroid with subclinical hypothyroidism, levothyroxine replacement therapy was accompanied by normal bone mass values. Conflict of interest: None declared. doi:10.1016/j.bone.2009.03.317
P406 Effects of selective serotonin reuptake inhibitors on bone mechanical properties in ovariectomized and non-ovariectomized rats J. Folwarczna*, M. Pytlik, B. Nowinska, U. Cegiela, P. Molin, T. Hanke, H.I. Trzeciak Department of Pharmacology, Medical University of Silesia, Sosnowiec, Poland
S407
Administration of selective serotonin reuptake inhibitors (SSRIs), drugs used in the treatment of depression, may be associated with the increased risk of fracture. SSRIs are often prescribed to postmenopausal women. There are a few experimental studies on fluoxetine skeletal effects. To our knowledge, the effects of other SSRIs on bones have not been studied in experimental conditions. The aim of the present study was to investigate how SSRIs (fluoxetine and fluvoxamine) affect the skeletal system of female rats and whether their possible effects depend on estrogen status. The experiments were carried out on 15–17-week-old Wistar rats. The effects of fluoxetine hydrochloride (10 mg/kg p.o.) and fluvoxamine maleate (30 mg/kg p.o.) on bones of normal nonovariectomized rats, bilaterally ovariectomized (OVX, estrogendeficient) rats and OVX rats supplemented with estradiol (0.2 mg/ kg p.o.), in comparison with appropriate control groups, were studied (n = 8–10 per group). The ovariectomy was performed 7–9 days before the start of a four-week period of daily administration of the drugs. Bone geometric parameters, mass, mass of bone mineral in the tibia, femur and L-4 vertebra, as well as mechanical properties of tibial metaphysis and femoral diaphysis in three-point bending tests and femoral neck in a compression test were assessed (Instron 3342 500N apparatus). In OVX control rats, the ratio of bone mineral mass to bone mass was decreased and mechanical properties of tibial metaphysis and femoral neck were worsened in comparison with sham-operated control rats. Supplementation with estradiol improved bone mineralization, but did not improve mechanical properties of bones in OVX rats. Fluoxetine worsened mechanical properties of the tibial metaphysis both in OVX and non-ovariectomized rats; moreover, it decreased bone mass and mass of bone mineral (not affecting the bone mineral/bone mass ratio) in OVX rats. Fluoxetine did not significantly affect mechanical properties of the femoral neck and diaphysis. Fluvoxamine did not affect bone mass, mineralization and mechanical properties in female rats. Concluding, effects of the investigated SSRIs on rat bone mechanical properties do not depend on estrogen status. Results of the present study also indicate that the skeletal effects of different SSRIs should be considered separately. Acknowledgments: This study was supported by grant No N401 059 32/1412 from the Ministry of Science and Higher Education, Poland. Conflict of interest: None declared. doi:10.1016/j.bone.2009.03.318
P407 Serotonin effects on the skeletal system may depend on estrogen status: Differential effects on bone mechanical properties in non-ovariectomized and ovariectomized rats J. Folwarczna*, T. Hanke, P. Molin, H.I. Trzeciak Department of Pharmacology, Medical University of Silesia, Sosnowiec, Poland Serotonin has been recently reported to be involved in regulation of bone metabolism in vitro and in vivo. Estradiol has been shown to interact with serotonergic system. The aim of the present study was to investigate how elevated peripheral levels of serotonin or inhibition of serotonin synthesis by p-chlorophenylalanine affects the skeletal system of female rats and whether the serotonin effects on bones depend on estrogen status. The experiments were carried out on 15–17-week-old Wistar rats. The effects of serotonin (serotonin creatinine sulfate complex, 10 mg/ kg/day, s.c.) and p-chlorophenylalanine (a tryptophan hydroxylase inhibitor, 100 mg/kg/day, i.p.) on bones of normal non-ovariecto-