Biomedical subjects

J K Yeh

Publications and source records attributed to J K Yeh.

At least 19 recordsLinked to original sources

PubMed2006

Synergistic effect of vitamin K2 and prostaglandin E2 on cancellous bone mass in hypophysectomized young rats.

Hypophysectomy (HX) results in cessation of bone growth and cancellous osteopenia in rats. It has been reported that prostaglandin E2 (PGE2) improves cortical and cancellous bone mass in HX rats. The purpose of the present study was to examine whether combined administration of vitamin K2 and PGE2 would have a more beneficial effect on bone than single administration of either alone in HX rats. Forty-three female Sprague-Dawley rats, 6 weeks of age, were randomized by the stratified weight method into five groups: intact controls, HX, HX + vitamin K2 (30 mg/kg, p.o., daily), HX + PGE2 (0.83 mg/kg, i.m., 5 days a week), and HX + vitamin K2 + PGE2. The duration of the experiment was 4 weeks. There was a reduction in cancellous bone volume/total tissue volume (BV/TV) of the proximal tibial metaphysis and a reduction in total tissue area and cortical area (Ct.Ar) of the tibial diaphysis. Vitamin K2 did not affect cancellous BV/TV or Ct.Ar. On the other hand, PGE2 attenuated the loss of cancellous BV/TV in association with higher bone formation rate/bone surface (BFR/BS) and eroded surface (ES)/BS compared with intact controls. PGE2 also increased percent Ct.Ar compared with nontreated HX rats as a result of attenuation of a decrease in periosteal BFR/BS. Vitamin K2 had a synergistic effect with PGE2 on cancellous BV/TV as a result of the suppression of an increase in ES/BS observed by PGE2 treatment. These results suggested that PGE2 had an anabolic action on cancellous and cortical bone and that despite no apparent effect of vitamin K2 on bone, it had a synergistic effect with PGE2 on cancellous bone mass in young HX rats.

Animals↗

PubMed2005

Raloxifene and vitamin K2 combine to improve the femoral neck strength of ovariectomized rats.

We evaluated the skeletal effects of two osteoporosis therapies in an ovariectomized rat model, raloxifene and vitamin K2, as well as the vitamin K2 plus raloxifene (K + Ral) combination. In two studies, 6-month-old rats were ovariectomized, except for sham-ovariectomy controls (Sham), and dosed orally with vehicle, 30 mg/kg vitamin K2, 1 mg/kg raloxifene, or the combination of K + Ral for 6 weeks following surgery. Vitamin K2 had no effect on serum estrogen, low-density lipoprotein cholesterol (LDL-C), or urinary deoxypyridinoline levels, but slightly increased osteocalcin levels compared to Ovx. Raloxifene lowered total cholesterol, LDL-C, osteocalcin, and urinary deoxypyridinoline levels to below Ovx levels, while having no effect on estrogen levels. Raloxifene, but not vitamin K2, prevented ovariectomy-induced loss of bone in the distal femoral metaphysis and proximal tibial metaphysis, as did the K + Ral combination. Raloxifene, but not vitamin K2, partially prevented, loss of vertebral bone mineral density (BMD), whereas K + Ral had BMD greater than that of Ovx. Vitamin K2 increased bone formation rate to above Ovx, whereas raloxifene and K + Ral reduced bone formation rate to Sham levels. Vitamin K2 had no effect on eroded surface compared to Ovx, while raloxifene and K + Ral reduced eroded surface to Sham levels. Groups were not different in the BMD of femoral midshaft; however vitamin K2 was observed to increase periosteal mineralizing surface of the tibial shaft to above Ovx, while raloxifene reduced periosteal mineralizing surface toward Sham levels. Femoral neck strength was not different between groups, indicating no significant beneficial effect of either raloxifene or vitamin K2 at this site. However, K + Ral had reproducibly greater femoral neck strength than Ovx or Sham. Raloxifene, but not vitamin K2, partially prevented loss of lumbar vertebra strength; but K + Ral was not different from Sham or Ovx. Therefore, raloxifene and vitamin K2 had complementary effects on bone resorption and formation activities, respectively, resulting in a reproducible, significant improvement of femoral neck strength. These rat data suggest interesting therapeutic possibilities that may require clinical verification.

Administration, Oral↗

PubMed2005

Effects of vitamin K2 administration on calcium balance and bone mass in young rats fed normal or low calcium diet.

OBJECTIVE: The purpose of this study was to examine the effects of vitamin K2 administration on calcium balance and bone mass in young rats fed a normal or low calcium diet. METHODS: Forty female Sprague-Dawley rats, 6 weeks of age, were randomized by stratified weight method into four groups with 10 rats in each group: 0.5% (normal) calcium diet, 0.1% (low) calcium diet, 0.5% calcium diet + vitamin K2 (menatetrenone, 30 mg/100 g chow diet), and 0.1% calcium diet + vitamin K2. After 10 weeks of feeding, serum calcium and calciotropic hormone levels were measured, and intestinal calcium absorption and renal calcium reabsorption were evaluated. Bone histomorphometric analyses were performed on cortical bone of the tibial shaft and cancellous bone of the proximal tibia. RESULTS: Feeding a low calcium diet induced hypocalcemia, increased serum parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D [1,25(OH)2D] levels with decreased serum 25-hydrovyvitamin D [25(OH)D] level, stimulated intestinal calcium absorption and renal calcium reabsorption, and reduced cortical bone mass as a result of decreased periosteal bone gain and enlarged marrow cavity, but did not significantly influence cancellous bone mass. Vitamin K2 administration in rats fed a low calcium diet stimulated renal calcium reabsorption, retarded the abnormal elevation of serum PTH level, increased cancellous bone mass, and retarded cortical bone loss, while vitamin K2 administration in rats fed a normal calcium diet stimulated intestinal calcium absorption by increasing serum 1,25(OH)2D level, and increased cortical bone mass. CONCLUSION: This study clearly shows the differential response of calcium balance and bone mass to vitamin K2 administration in rats fed a normal or low calcium diet.

Animals↗

PubMed2004

Effects of vitamin D supplementation on calcium balance and bone growth in young rats fed normal or low calcium diet.

OBJECTIVE: We examined the effect of vitamin D supplementation on bone growth in young rats fed a normal or low calcium diet. METHODS: Fifty female Sprague-Dawley rats, 6 weeks of age, were randomized by stratified weight method into five groups with 10 rats in each group: baseline control, 0.5% (normal) or 0.1% (low) calcium diet, and 0.5 or 0.1% calcium diet + vitamin D (25 microg/100 g, food intake). Duration of the experiment was 10 weeks. RESULTS: Vitamin D supplementation stimulated intestinal calcium absorption and increased urinary calcium excretion in rats fed a low or normal calcium diet. Vitamin D supplementation prevented the reduction in periosteal bone gain but enhanced enlargement of the marrow cavity and reduced the maturation-related cancellous bone gain in rats fed a low calcium diet, and increased the maturation-related cancellous and cortical bone gains in rats fed a normal calcium diet. CONCLUSION: This study shows the differential effects of vitamin D supplementation on born growth in young rats fed a normal or low calcium diet.

Animals↗

PubMed2003

RETRACTED: Comparative effects of vitamin K and vitamin D supplementation on prevention of osteopenia in calcium-deficient young rats.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. The Journal has been made aware of concerns regarding the integrity of the data, authorship and ethical approval for this study. Despite repeated attempts to contact the co-authors we have been unable to confirm the authorship of this paper.

Animals↗

PubMed2001

Prevalence of porcine proliferative enteropathy and its control with tylosin in Korea.

Porcine proliferative enteropathy(PPE) is an enteric disease been caused by Lawsonia intracellularis. It has become one of the critical problems in the pig industry. To investigate the prevalence of PPE in Korea, serum samples of 828 pigs from 65 herds were tested using indirect immunofluorescence antibody technique(IFA). The infection rate in individual pigs varied from 44 to 69%, whereas 100% in pig farms. The infection frequency was 57, 44.9, and 59.4% according to age respectively. Administration of tylosin in feed at a concentration of 110 ppm for 14 days reduced the infection rate of the farms. These data indicated that the high prevalence of PPE may be controlled by tylosin.

Administration, Oral↗

PubMed2001

Effect of circular motion exercise on bone modeling and bone mass in young rats: an animal model of isometric exercise.

The aims of the study are to develop a non-invasive animal model of circular motion exercise and to evaluate the effect of this type of exercise on bone turnover in young rats. The circular motion exercise simulates isometric exercise using an orbital shaker that oscillates at a frequency of 50 Hz and is capable of speeds from 0-400 rpm. A cage is fixed on top of the shaker and the animals are placed inside. When the shaker is turned on, the oscillatory movement should encourage the animals to hold on to the cage and use various muscle forces to stabilize themselves. Rats at 8 weeks of age were trained on the shaker for 6 weeks and static and dynamic histomorphometric analyses were performed for the proximal tibial metaphysis and the tibial shaft. The exercise resulted in no significant effect on animal body weight, gastrocnemius muscle weight and femoral weight. Although the bone formation rate of cancellous and cortical periosteum was increased by the exercise, trabecular bone volume was decreased. The exercise increased periosteal and marrow perimeters and the cross-sectional diameter of cortical bone from medial to lateral without a significant increase in the cortical bone area. These results suggest that circular motion exercise under force without movement or additional weight loading will cause bone-modeling drift with an increase in bone turnover to reconstruct bone shape in adaptation to the demand in strength. Since there is no additional weight loading during circular motion exercise, the net mass of bone is not increased. The bone mass lost in trabecular bone could possibly be due to a re-distribution of mineral to the cortical bone.

Journal Article↗

PubMed2000

Osteoblast-like cells of the hypophysectomized rat: a model of aberrant osteoblast development.

In a previous work, we demonstrated that the osteoprogenitors derived from the marrow stroma of the hypophysectomized (HX) rat demonstrate enhanced proliferative and differentiation capacities when placed in an optimal microenvironment. In this study, we sought to investigate the potential of the trabecular osteoblast-like cells of the HX rat. These cells represent a more mature pool of osteoblasts than the progenitors derived from the marrow stroma. We examined all three stages of osteoblast development using trabecular osteoblast-like cells derived from age-matched intact rats as a control. Using thymidine incorporation and cell number as indicators of proliferation, we found that these cells, like the osteoprogenitors derived from the HX rat, demonstrate augmented proliferation when placed in culture. Additionally, type I collagen expression remained at significant levels past the end stages of proliferation, at which point it is expected to be downregulated. Matrix maturation markers, such as alkaline phosphatase activity and bone sialoprotein expression, however, were significantly lower than in the controls. Mineralization potential, as measured by mineralized nodule formation, Ca(2+) content, and OPN and OCN expression, was also significantly reduced. Our results have uncovered an aberrant model of osteoblast development in which proliferation is deregulated, resulting in a minimal capacity of these cells to develop into fully differentiated mineralizing osteoblasts.

Animals↗

PubMed2000

Effect of deconditioning on cortical and cancellous bone growth in the exercise trained young rats.

Exercise enhances bone growth and increases peak bone mass. The aim of this study was to determine whether or not 4 weeks of deconditioning after 8 weeks of exercise in growing rats would result in a decrease in bone gain or reverse the benefits of exercise. Fifty 4-week-old female Sprague-Dawley rats were randomized by a stratified weight method into 5 groups with 10 rats in each group: 8 weeks exercise (8EX), 8 weeks sedentary control (8S), 12 weeks exercise (12EX), 8 weeks exercise followed by 4 weeks sedentary (8EX4S), and 12 weeks sedentary control (12S). The exercise consisted of running on a treadmill with a 5 degrees slope at 24 m/minute for 1 h/day and 5 days/week. After each period of exercise, cancellous and cortical bone histomorphometry were performed on double fluorescent labeled 5-microm-thick sections of the proximal tibia and 40-microm-thick sections of the tibial shaft, respectively. Eight and 12 weeks of exercise resulted in a significant increase in the body weight and gastrocnemius muscle weight by two-way analysis of variance (ANOVA). The femoral wet weight (mg; mean +/- SD; 8EX, 781 +/- 45.1 vs. 8S, 713 +/- 40.5; p < 0.05; 12EX, 892 +/- 41.6 vs. 12S, 807 +/- 19.8; p < 0.05) was significantly higher in the exercise group than that in the respective control groups. The femoral wet weight and bone volume (BV) of the 8EX4S group (818 +/- 46.2 mg and 531 +/- 31.2 microl, respectively) were significantly lower than those of the 12EX group (p < 0.05) and did not differ significantly from those of the 12S groups. The cancellous BV was significantly higher in the 8EX and 12EX groups than that in the respective sedentary groups (p < 0.05). The cortical bone area of the tibial shaft was also significantly higher in the 12EX than that in the 12S group (p < 0.05). The increase in the cancellous BV or cortical bone area was caused by an increase in the mineral apposition rate (MAR), without a significant effect in the labeled perimeter. The bone formation rate (BFR; microm3/microm2 per day) in the cancellous bone (12EX, 27.9 +/- 7.74 vs. 12S, 15.4 +/- 4.56; p < 0.05) or periosteal surface (12EX, 127.6 +/- 27.7 vs. 12S, 79.5 +/- 18.6; p < 0.05) was significantly higher in the exercised groups than that in the respective control group (p < 0.05). Again, deconditioning resulted in a decrease in the cancellous BFR, BV, periosteal BFR, and cortical bone area to levels not significantly different from the 12S group. In conclusion, our findings showed that exercised growing rats, when deconditioned, lost the benefits gained through exercise and their bone parameters were reduced to levels not different from the sedentary control. Thus, continued exercise is required to maintain high bone mass.

Animals↗

PubMed1999

Differential effect of treadmill exercise on three cancellous bone sites in the young growing rat.

The aim of the present study was to examine cancellous bone changes induced by exercise on three different skeletal sites, the lumbar vertebra, the proximal, and the distal tibia, in the young growing rat. Forty 4-week-old female Sprague-Dawley rats were randomized into 4 groups of 10 animals each; 8 weeks exercise (8EX), 8 weeks sedentary control (8CON), 12 weeks exercise (12EX), and 12 weeks sedentary control (12CON). The exercise regimen consisted of treadmill running at 24 m/min 1 hr per day 5 days a week. After each period of exercise, the proximal and distal tibial metaphyses (PTM and DTM, respectively) and the fifth lumbar (L5) vertebral body were processed for histomorphometry of the cancellous bone (secondary spongiosa) and cortical periosteum. Eight and twelve weeks of exercise significantly increased the mineral apposition rate and bone formation rate in the PTM and DTM, and 12 weeks of exercise significantly increased the labeled perimeter in the DTM, compared with the age-matched controls. Eight and twelve weeks of exercise significantly increased cancellous bone volume in the PTM (mean +/- standard deviation, 8EX; 19.1 +/- 2.9% vs 8CON; 14.3 +/- 3.1%, P < 0.05 and 12EX; 18.8 +/- 3.5% vs 12CON; 15.2 +/- 3.3%, P < 0.05), and 12 weeks exercise significantly increased cancellous bone volume in the DTM, compared with age-matched control (12EX; 32.5 +/- 7.7%, 12CON; 22.2 +/- 4.8%, P < 0.05). The increase in cancellous bone volume by 12 weeks exercise was higher in the DTM than that in the PTM (43.4% and 24.0%, respectively). On the other hand, the exercise did not significantly affect cancellous bone volume and bone formation in the L5 vertebral body, although the cortical periosteal bone formation rate and the L5 vertebral bone mass were increased. These findings suggest that cancellous bone adaptation to treadmill exercise is site specific, and the effect may be influenced by factors such as mechanical loading and metaphyseal bone architecture in the young growing rat.

Adaptation, Physiological↗

PubMed1999

Effects of growth hormone and testosterone on cortical bone formation and bone density in aged orchiectomized rats.

Osteoporosis in men is a disease that is increasing in incidence, and with an increasing elderly population it poses a serious health problem. Since both testosterone (T) and growth hormone (GH) have an anabolic effect on bone and both decrease with aging, we were prompted to test whether the administration of these hormones in combination would increase bone mass in orchiectomized (orx) senile rats more than administration of either agent alone. Twenty-month-old male Wistar rats were divided into five groups with seven animals each: (a) age-matched intact control, (b) orx, (c) orx+GH (2.5 mg/kg/day), (d) orx+T [10 mg/kg, subcutaneous (s.c.), injection given twice a week], and (e) orx+GH+T. Testosterone and GH were given subcutaneously for 4 weeks. Bone histomorphometry of the tibial shaft showed that the orx group had lower cortical bone area than the intact control group. The decrease in cortical bone area was due to increased intracortical porosis as well as decreased periosteal bone formation rate (BFR). Administration of T to the orx animals prevented the development of the porosis and the decrease in periosteal BFR. The bone mineral content (BMC) and bone mineral density (BMD) of the femur as tested by dual-energy X-ray absorptiometry were significantly higher in the orx+T than in the orx group and were not significantly different from that of the intact control group. Administration of GH to the orx rats increased periosteal BFR significantly; however, the BMC and BMD measured were not increased significantly in comparison to the orx group. When GH and T were combined in treatment, the cortical bone area, periosteal BFR, and femoral BMD were all significantly higher than that of the orx and even higher than the intact control rats. Two-way analysis of variance shows that the individual effect of GH and T treatment on the periosteal BFR and cortical bone area was significant. The effect of T, but not GH, on femoral BMC and BMD was also significant; however, there is no synergistic interaction between the two treatments. Four weeks of orx with or without GH or T administration had no significant effect on tibial metaphyseal cancellous bone volume. In conclusion, this short-term study suggests that the combined intervention of GH and T in androgen-deficient aged male rats may have an independent effect in preventing osteopenia. The significant effect of GH+T may be attributed to the prevention of intracortical porosis, and an increase in periosteal bone formation and cortical bone mass.

Absorptiometry, Photon↗

PubMed1999

Effect of hypophysectomy on the proliferation and differentiation of rat bone marrow stromal cells.

Conditions such as estrogen deficiency, skeletal unloading, and aging have all been demonstrated to have various effects on the proliferation and differentiation of bone marrow stroma-derived osteoprogenitor cells. Here we have sought to examine the effects of pituitary hormone deficiency on the proliferation and the differentiation of these osteoprogenitor cells using the hypophysectomized (HX) rat as a model. In the present study, we use an in vitro culture system to examine the effects of HX on the osteogenic potential of rat bone marrow stroma. With the intact animal as a control, we used [3H]thymidine incorporation and cell number as indexes of proliferation. We also measured alkaline phosphatase enzyme activity, relative levels of osteocalcin expression with RT-PCR, and osteopontin and bone sialoprotein steady-state levels by Northern blot to delineate the effect on differentiation. Our results indicate that osteoprogenitor cells exposed to a pituitary hormone-deficient environment in vivo demonstrate an enhanced proliferative capacity and also exhibit an augmented expression of differentiation markers when exposed to an optimal environment in vitro.

Animals↗

PubMed1999

Vitamin D supplementation in postmenopausal black women.

Black women have lower levels of serum 25-hydroxyvitamin D (25OHD) with higher serum PTH levels than white women. Correction of these alterations in the vitamin D-endocrine system could lead to less bone loss in postmenopausal women and, consequently, preservation of bone mass. Ten healthy postmenopausal black women were given 20 microg vitamin D3 daily for 3 months. At the end of the study, mean serum 25OHD levels had increased from 24 to 63 nmol/L. Serum intact PTH and nephrogenous cAMP declined significantly, and there was a 21% drop in the fasting urinary N-telopeptide of type I collagen. Vitamin D3 supplementation raises serum 25OHD levels in postmenopausal black women, decreases secondary hyperparathyroidism, and reduces bone turnover. These findings should spur further investigation of the use of vitamin D supplementation in the prevention of osteoporosis in this population.

Aged↗

PubMed1998

Anabolic effect of prostaglandin E2 in bone is not dependent on pituitary hormones in rats.

Prostaglandin E2 (PGE2) is an anabolic agent of bone in vivo but the mechanism of its action still remains unclear. The aim of this study was to determine whether the effect of PGE2 on skeleton is mediated by pituitary hormones. Forty female, Sprague-Dawley rats were divided into four groups: baseline control (basal), age-matched intact control (CON), hypophysectomy (HX), and HX + PGE2 (2 mg/kg/day) with 10 animals in each group. The basal group was sacrificed at 2 months of age, and the remaining groups after 6 weeks of treatment. Cancellous and cortical bone histomorphometry was performed on double fluorescent-labeled 40 micron-thick sections of the proximal tibia and tibial shaft. Our results show that HX resulted in a cessation of bone growth, a decrease in cancellous bone volume, and cortical bone gain compared with the age-matched, intact CON rats. Compared with the HX group, the HX + PGE2 group had a significantly greater tibial bone density (mean +/- SE, HX + PGE2:1.595 +/- 0.007 versus HX:1.545 +/- 0.013), percent cancellous bone volume (21.4 +/- 2.0 versus 8.41 +/- 1.70), percent cortical bone area (87.2 +/- 0.85 versus 81.7 +/- 0.7), and ratio of cortical area to marrow area (7.14 +/- 0.56 versus 4.52 +/- 0.21). Increased bone masses by PGE2 in the HX animals were accompanied by an increase in the trabecular and endosteal-labeled surface and bone formation rate. The trabecular number and width were increased whereas trabecular separation was decreased in the HX + PGE2 group compared with the HX group (P < 0.05). PGE2 treatment also caused a decrease in the tibial endosteal eroded surface and medullar cavity of the HX animals. In conclusion, this study clearly demonstrates that PGE2 (2 mg/kg/day) in the HX rats increases both cortical and cancellous bones and improves trabecular architecture in the tibia after 6 weeks of treatment. These skeletal alterations are due to a stimulation of bone formation and a suppression of bone resorption activity. These findings suggest that the anabolic effect of PGE2 in bone is independent of pituitary hormones.

Animals↗

PubMed1998

Biochemical and hormonal variables in black and white women matched for age and weight.

Weight and age may influence the levels of indexes of bone remodeling and the calciotropic hormones. In a study of interracial differences in these women, our black population was heavier than our white population. We therefore matched a subset of 96 black and 96 white women from our larger population for age and weight to determine whether a racial difference exists independent of the effects of weight and age. In addition, we were able to measure other indexes of bone remodeling (N-telopeptide of cross-linked collagen and pyridinoline cross-links), as well as hormones that may influence calcium metabolism (insulin-like growth factor-1 (IGF-1), insulin, calcitonin, and gastrin) in this subset. All indexes of bone remodeling were lower in black women. Black postmenopausal women had lower serum levels of calcidiol and higher parathyroid hormone (PTH) levels. The higher bone mass of black women is associated with lower bone remodeling in the presence of skeletal resistance to PTH. Serum IGF- 1, insulin, and calcitonin levels did not differ significantly between races. Serum gastrin levels were higher in black women. The higher levels of gastrin in black women should be investigated further for its possible effect on the absorption of calcium salts.

Adult↗

PubMed1997

Histologic evidence: growth hormone completely prevents reduction in cortical bone gain and partially prevents cancellous osteopenia in the tibia of hypophysectomized rats.

BACKGROUND: In previous studies we found that the cause of bone loss in young hypophysectomized (HX) animals was due primarily to an inhibition in growth-dependent bone gain and a decrease in bone turnover. The aim of this study was to determine whether growth hormone, which has stimulatory effects on bone growth and turnover, can prevent HX-induced skeletal alterations in rats. METHODS: Female Sprague-Dawley rats were divided into baseline control (BASAL), age-matched control (CON), HX, HX plus low-dose GH (1.5 mg/kg/d, subcutaneously), and HX plus high-dose GH (4.5 mg/kg/d) groups. The BASAL group was sacrificed at 2 months of age and the remaining groups were sacrificed after 6 weeks of treatment. Cancellous and cortical bone histomorphometry was performed on double-fluorescent-labeled 40 microm-thick sections of the proximal tibia and tibial shaft. RESULTS: Both low- and high-dose GH prevented the HX-induced decrease of IGF-I serum levels. High-dose GH also significantly increased the body weight and the wet weight of the gastrocnemius muscle when compared to the CON groups. In the tibial shaft, the periosteal labeled surface, mineral apposition rate and bone formation rate were higher in both of the GH-treated groups than in the HX group (P < 0.05). The tissue area and cortical bone area of the high-dose GH-treated rats were greater than those of the HX rats, but did not differ from those of the CON rats. In the proximal tibia, both low- and high-dose GH prevented an HX-induced decrease in the longitudinal growth rate and growth plate width, and increased surface-based bone formation compared to the HX and CON. Cancellous bone volume, tissue-based bone formation rate, and eroded surface in both of the GH-treated groups were higher than those of the HX group, but lower than those of the BASAL and CON groups (P < 0.05). Bone architecture of the HX rats was also improved after GH treatment. CONCLUSIONS: This study clearly demonstrates that GH replacement at the dosage of 4.5 mg/kg/d can completely prevent the HX-induced reduction in cortical bone gain in the tibial shaft, but can only partially prevent cancellous osteopenia in the proximal tibia after six weeks.

Animals↗

PubMed1997

Effects of 17 beta-estradiol administration on cortical and cancellous bone of ovariectomized rats with and without hypophysectomy.

Pituitary hormones are essential for bone growth and bone turnover. Hypophysectomy (HX) diminishes mitogenesis and abolishes the high bone turnover rate induced by ovariectomy (OV). It is not known whether the suppressive effect of estrogen on bone resorption is diminished or abolished by HX. The present study investigates the effects of 17 beta-estradiol (E2) (20 micrograms/wk) on cortical and cancellous bone mass and bone turnover as measured by histomorphometry in HX + OV (HO) rats. Sprague-Dawley rats at 2 months of age were OV or HO and the experiment was performed over a 6 week period. Hypophysectomy + OV (HO) resulted in a cessation of periosteal bone formation, and longitudinal bone growth and a decrease in cancellous bone volume. The tibial dry weight and tibial density were significantly lower in the HO than in the intact or OV groups. Administration of E2 to HO rats partially prevented cancellous bone loss, whereas the same dosage of E2 fully prevented cancellous bone loss in rats with OV alone. Nevertheless, cancellous bone volume was higher in the HO + E2 than in the HO-alone groups. Estradiol administration in HO rats did not suppress cancellous bone formation rate or the eroded surface as much as it did in the OV rats. The suppressive effect of E2 on periosteal bone formation rate and mineral apposition rate was also diminished in HO rats. However, factorial ANOVA showed that the effects of E2 on increasing cancellous bone volume and decreasing periosteal bone formation rate and mineral apposition rate were still significant in the HO rats. Tibial dry weight and tibial density did not differ between HO and HO + E2 groups. In conclusion, we have demonstrated that the estrogen-induced effects of preventing cancellous bone loss, of suppressing bone formation, and resorption as seen in OV rats was diminished but not abolished in HO rats.

Animals↗

PubMed1997

Effects of estrogen and growth hormone on skeleton in the ovariectomized rat with hypophysectomy.

To investigate whether growth hormone (GH) and 17beta-estradiol (E2) replacement can prevent osteopenia induced by pituitary and ovarian hormone deficiency [by hypophysectomy and ovariectomy (HX+OV)], we administered relatively low doses of GH (2.3 IU x kg(-1) x day(-1)) and E2 (100 microg x kg(-1) x wk(-1)) in experiment 1 and relatively high doses of GH (13.5 IU x kg(-1) x day(-1)) and E2 (3,500 microg x kg(-1) x wk(-1)) in experiment 2 to 2-mo-old HX+OV Sprague-Dawley rats for 6 wk. Our data show that the HX+OV of rats results in diminished periosteal bone formation, longitudinal bone growth, and decreased cancellous bone volume. Administration of either the low or high dose of GH to these rats increased their systemic growth, serum levels of osteocalcin, and cortical bone formation. Either low or high doses of GH or E2 alone only partially prevent cancellous bone loss. However, the combined treatment of GH plus E2 resulted in an additive increase in the cancellous bone mass. We conclude that the additive effect of GH plus E2 on cancellous bone is attributed to the suppressive effect of E2 on bone resorption and the anabolic effect of GH on bone formation.

Animals↗