Johannes Eberle

Androgen Deficiency Induces High Turnover Osteopenia in Aged Male Rats: A Sequential Histomorphometric Study

Hypogonadism is considered to be one of the major risk factors for osteoporosis in men. However, the mechanisms of bone loss caused by androgen deficiency are still unclear. In the present study, we sequentially investigated the skeletal and hormonal effects of androgen deficiency in aged orchiectomized (ORX) rats over a time period of 9 months. One hundred seventy 13‐month‐old male Fischer‐344 rats were either ORX or sham‐operated (SHAM). Eight rats served as baseline controls. After in vivo fluorochrome labeling, groups of 8–15 SHAM and ORX rats each were killed at 2 weeks and at 1, 2, 3, 4, 6, and 9 months postsurgery. As expected, ORX induced a fall in serum total and free testosterone levels, but also reduced serum estradiol concentrations. Cancellous bone area (BAr) in the proximal tibia but not in the first lumbar vertebral body showed an age‐dependent decline in SHAM rats. Relative to SHAM controls, ORX rats had significantly reduced cancellous BAr after 2 weeks post‐ORX in the tibia and after 2 months post‐ORX in the vertebral body. Thereafter, vertebral and tibial cancellous BAr continued to decline in ORX animals throughout the study. Osteoclast number (NOc), osteoblast surface, bone formation rate (BFR), and activation frequency were increased in ORX animals from 1 month postsurgery until the end of the trial. Moreover, in close temporal association with the histomorphometric findings, serum osteocalcin and urinary excretion of collagen cross‐links and calcium were elevated in ORX rats. In a stepwise model of multiple regression analysis using estradiol and free and total testosterone as independent variables, estradiol was the only significant predictor of histomorphometric indices of bone formation and bone resorption in SHAM and ORX rats. These data show that androgen deficiency induces substantial loss of cancellous bone in the axial and appendicular skeleton of aged male rats and that this osteopenia is associated with a sustained increase in bone turnover. Thus, the skeletal effects of androgen withdrawal in aged male rats appear to resemble those induced by estrogen withdrawal in female rats. Furthermore, our study suggests that estradiol may act as a physiological suppressor of bone remodeling in aged male rats.

Skeletal effects of zinc deficiency in growing rats.

There is ample evidence that zinc plays an important role in bone metabolism and zinc deficiency has been implicated as a risk factor in the development of osteoporosis. It was the aim of the present study to investigate the skeletal effects of alimentary zinc deficiency in growing rats using quantitative bone histomorphometry. Twenty-four male Sprague Dawley rats with a mean initial body weight of 101 +/- 2 g were allocated in two groups of 12 rats each and had free access to a semi-synthetic, casein-based, zinc-deficient diet (0.76 mg zinc/kg) or to the same diet supplemented with 60 mg zinc per kg. All rats were sacrificed 42 days after the start of the experiment and the right distal femur was removed for bone histomorphometry. Relative to controls (+Zn), the zinc-deficient rats (-Zn) had a significantly lower body weight and about an 80% reduction in plasma and femur zinc concentration. The histomorphometric evaluation of the distal femoral metaphysis showed that zinc deficiency led to a 45% reduction (p < 0.01) in cancellous bone mass and to a deterioration of trabecular bone architecture, with fewer and thinner trabeculae. The osteopenia in -Zn rats was accompanied by significant reductions in osteoid perimeter (-31%, p < 0.05), osteoblast perimeter (-30%, p < 0.05), and osteoclast number (-38%, p < 0.01) relative to +Zn controls. We conclude that zinc deficiency induced low turnover osteopenia in femoral cancellous bone of growing rats. These results support the hypothesis that zinc deficiency during growth may impair the accumulation of maximal bone mass in humans; additionally, they suggest that zinc deficiency may play a role as a risk factor in the pathogenesis of osteoporosis.

Ovariectomy augments B lymphopoiesis and generation of monocyte-macrophage precursors in rat bone marrow

To investigate the effects of estrogen depletion on hematopoiesis and bone turnover, female rats were either ovariectomized (OVX) or sham operated and killed at 1, 2, 3, and 4 wk postsurgery. Flow cytometric analysis of bone marrow cells (BMC) revealed that, in close temporal association with the rise in bone turnover as measured by bone histomorphometry, the number of Thy 1.1+ and KiB1R+ BMC increased two- to threefold in OVX rats relative to sham controls. The Thy 1.1+ BMC were further characterized as Thy 1.1+/KiB1R+and Thy 1.1+/HIS24+double-positive cells of the B cell lineage. A transient rise in ED1+ myeloid cells expressing a lysosomal antigen specific for the monocyte-macrophage and osteoclast lineage coincided with the upregulation of osteoclast numbers in OVX rats at 2 wk postsurgery, but the number of ED8+ myelomonocytic BMC remained unchanged. Administration of estradiol prevented the rise in Thy 1.1+, KiB1R+, and ED1+ BMC in OVX animals. Our study indicates that ovariectomy upregulates B lymphopoiesis in rat bone marrow and increases myeloid cell differentiation into the monocyte-macrophage and possibly also the osteoclast lineage.

Cortical Bone Loss in Androgen-Deficient Aged Male Rats Is Mainly Caused by Increased Endocortical Bone Remodeling†

Introduction: Hypogonadism is considered to be one of the major risk factors for osteoporosis in men. Here, we sequentially studied the effects of androgen deficiency on cortical bone in aged orchiectomy (ORX) rats.

Hämatologische Veränderungen bei alimentärem Pb-Mangel wachsender Ratten

The effect of an alimentary Pb-deficiency on hematological parameters was examined in two growth- and one generation-experiments with female Sprague Dawley rats. The animals were fed a semisynthetic casein-based diet supplemented with 0 ppb up to 800 ppb Pb as Pb-II-acetate-3-hydrate. In two experiments the blood parameters of the rats of G0-generation fed the diet poor in Pb were changed to a normocytic, normochrome pancytopenia at day 21 resp. 28 of the experiments. At day 28 resp. 41 the blood parameters normalized resp. the different Pb-supply in the diet only effected the mean corpuscular volume- and mean corpuscular hemoglobin-values. It was assumed that the disturbances in blood parameters at deficient Pb-supply are caused by temporary hemolysis.ZusammenfassungDer Einfluß eines alimentären Pb-Mangels auf hämatologische Kenngrößen wurde in zwei Wachstumsversuchen und einem Generationenversuch mit weiblichen Sprague Dawley Ratten untersucht. Die Tiere erhielten eine halbsynthetische Diät auf Caseinbasis, die sich nur in der Konzentration an zugelegtem Blei in Form von Pb-II-acetat-3-hydrat unterschied (0 ppb Pb bis 800 ppb Pb). In zwei Versuchen war bereits in der G0-Generation das Blutbild der Pb-arm versorgten Tiere am Versuchstag 21 bzw. 28 im Sinne einer normocytären, normochromen Panzytopenie verändert. Am 28. bzw. 41. Versuchstag hatten sich die Blutbilder normalisiert bzw. lösten die unterschiedlichen Pb-Zulagen in der Diät nur noch Veränderungen der Werte des mittleren corpuskulären Volumens und des mittleren corpuskulären Hämoglobingehalts aus. Als Ursache für die Störungen im Blutbild bei mangelnder Pb-Versorgung ist eine temporär auftretende Hämolyse am wahrscheinlichsten.SummaryThe effect of an alimentary Pb-deficiency on hematological parameters was examined in two growth- and one generation-experiments with female Sprague Dawley rats. The animals were fed a semisynthetic casein-based diet supplemented with 0 ppb up to 800 ppb Pb as Pb-II-acetate-3-hydrate. In two experiments the blood parameters of the rats of G0-generation fed the diet poor in Pb were changed to a normocytic, normochrome pancytopenia at day 21 resp. 28 of the experiments. At day 28 resp. 41 the blood parameters normalized resp. the different Pb-supply in the diet only effected the mean corpuscular volume- and mean corpuscular hemoglobin-values. It was assumed that the disturbances in blood parameters at deficient Pb-supply are caused by temporary hemolysis.

Untersuchungen zur Knochenmarksmorphologie und zu verschiedenen Hämolysemarkern bei wachsenden Ratten im alimentären Bleimangel

The effects of an alimentary lead deficiency on bone marrow morphology and several laboratory parameters of hemolysis were examined in two growth- and one generation-experiments with female Sprague Dawley rats. The animals were fed a semisynthetic casein-based diet supplemented with 0 ppb up to 800 ppb lead as Pb-II-acetat-3-hydrate. The evaluation of bone marrow did not show differences among the groups with different lead supply in the diet. Concerning the laboratory parameters of hemolysis it has been shown that the hemoglobin concentration of plasma and the lactate-dehydrogenase activity of serum were increased and the haptoglobin concentration of serum was decreased in the groups fed the diets poor in lead relative to lead-adequate animals. The activity of glutathione peroxidase and the glutathione concentration in red blood cells were increased in the groups fed the lead-deficient diet compared to lead-adequate groups. In conclusion, the study shows that the pancytopenia observed recently in lead-deficient rats is not caused by disturbed hematopoesis, whereas some parameters measured suggest that there exists increased hemolysis in lead-deficient rats.ZusammenfassungDer Einfluß eines alimentären Bleimangels auf die Knochenmarksmorphologie und verschiedene Hämolysemarker im Serum wurde in zwei Wachstumsversuchen und einem Generationenversuch mit weiblichen Sprague Dawley Ratten untersucht. Die Tiere erhielten eine halbsynthetische Diät auf Caseinbasis, die sich nur in der Konzentration an zugelegtem Blei in Form von Pb-II-acetat-3-hydrat unterschied (0 ppb Pb bis 800 ppb Pb). Die Knochenmarksuntersuchungen ergaben einen völlig unauffälligen Befund und zeigten keine Unterschiede zwischen den unterschiedlichen Blei-Zulagestufen. Bei den Hämolysemarkern deutete sich im Bleimangel eine Erhöhung des freien Hämoglobins im Plasma sowie der Aktivität der Laktatdehydrogenase im Serum und eine Erniedrigung der Konzentration des Haptoblobins im Serum an. Weiterhin war die Aktivität der Glutathionperoxidase und die Konzentration des Glutathions in den Erythrozyten in den bleiarm versorgten Gruppen erhöht. Insgesamt zeigt die Untersuchung, daß die in einer früheren Untersuchung bei Bleimangelratten aufgetretene Panzytopenie nicht auf eine Störung der Blutzellbildung zurückzuführen sein dürfte, während sich aufgrund der gemessenen Hämolysemarker ansatzweise Anhaltspunkte für eine vermehrte periphere Hämolyse ergaben.SummaryThe effects of an alimentary lead deficiency on bone marrow morphology and several laboratory parameters of hemolysis were examined in two growth- and one generation-experiments with female Sprague Dawley rats. The animals were fed a semisynthetic casein-based diet supplemented with 0 ppb up to 800 ppb lead as Pb-II-acetat-3-hydrate. The evaluation of the bone marrow did not show differences among the groups with different lead supply in the diet. Concerning the laboratory parameters of hemolysis it has been shown that the hemoglobin concentration of plasma and the lactate-dehydrogenase activity of serum were increased and the haptoglobin concentration of serum was decreased in the groups fed the diets poor in lead relative to lead-adequate animals. The activity of glutathione peroxidase and the glutathione concentration in red blood cells were increased in the groups fed the lead-deficient diet compared to lead-adequate groups. In conclusion, the study shows that the pancytopenia observed recently in lead-deficient rats is not caused by disturbed hematopoesis, whereas some parameters measured suggest that there exists increased hemolysis in lead-deficient rats.