H. Weiser

Vitamin D metabolites prevent vertebral osteopenia in ovariectomized rats

SummaryThe present study investigated the prophylactic effects of vitamin D metabolites and vitamin D metabolite combinations on static and dynamic, tetracycline-based, histomorphometric parameters in the axial skeleton of ovariectomized rats. Forty-three Fischer-344 rats (10 weeks old, 130 g each body weight, BW) were either bilaterally ovariectomized (OVX) or sham-operated (SHAM). The rats were allocated into the following groups: SHAM; OVX; OVX+7.5 ng 1α,25-dihydroxyvitamin D3 [1,25(OH)2D3]/rat/day; OVX +15 ng 1α,24R,25-trihydroxyvitamin D3 [1,24,25-(OH)3D3]/rat/day; OVX+75 ng 24R,25-dihydroxyvitamin D3 [24,25(OH)2D3]/rat/day; OVX+7.5 ng 1,25(OH)2D3/rat/ day+15 ng 1,24,25(OH)3D3/rat/day; OVX+7.5 ng 1,25(OH)2D3/rat/day+75 ng 24,25(OH)2D3/rat/day. The vitamin D metabolites were fed orally starting 4 weeks after surgery. Urine and blood samples were collected 12 and 16 weeks postovariectomy, respectively. Sixteen weeks after surgery, all rats were sacrificed, and the first lumbar vertebrae were processed undecalcified for histomorphometric analysis. Ovariectomy induced a highly significant reduction (P<0.001) of cancellous bone mass in the secondary spongiosa of the lumbar vertebral body. The bone loss in OVX rats was accompanied by a distinct elevation of all histomorphometric parameters of bone formation and resorption. 1,25(OH)2D3 and both vitamin D metabolite combinations significantly raised serum calcium levels and prevented the bone loss by inhibiting the increased bone resorption in OVX rats. In the applied dosage, 1,24,25(OH)3D3 and 24,25(OH)2D3 alone were ineffective in preserving the cancellous bone of the lumbar vertebra in OVX rats. We conclude that the oral prophylactic application of low doses of active vitamin D metabolites can effectively prevent the osteopenia induced by ovariectomy in the axial skeleton of the rat.

Role of vitamin D metabolites in the prevention of the osteopenia induced by ovariectomy in the axial and appendicular skeleton of the rat.

SummaryForty Fischer-344 rats (10 weeks old, 130 g BW) were either bilaterally ovariectomized (OVX) or sham-operated (SHAM). The rats were allocated to the following groups: SHAM; OVX; OVX + 15 ng 1α,25-dihydroxyvitamin D3 [1,25(OH)2D3]/rat/d; OVX + 30 ng 1α,24R,25-trihydroxyvitamin D3 [1,24,25(OH)3D3]/ rat/d; OVX + 15 ng 1,25(OH)2D3/rat/d + 30 ng 1,24,25(OH)3D3/rat/d. The vitamin D metabolites were fed orally starting 4 weeks after surgery. Urine and blood samples were taken at several time points during the experiment. Twenty-one weeks after surgery all rats were sacrificed, and the proximal tibiae and the first lumbar vertebrae were processed undecalcified for static bone histomorphometry.Ovariectomy induced a 40% reduction in vertebral cancellous bone area, and a 69% reduction in tibial cancellous bone area. This bone loss in OVX rats was associated with moderately increased biochemical and histomorphometric indices of bone formation and resorption as compared to values in sham-operated animals. Through inhibition of bone resorption, treatment of OVX rats with 1,25(OH)2D3, 1,24,25(OH)3D3, and the metabolite combination prevented the ovariectomyinduced osteopenia in the lumbar vertebra, and partially prevented cancellous bone osteopenia in the tibial metaphysis. However, OVX rats receiving 1,25(OH)2D3 alone or in combination with 1,24,25(OH)3D3 exhibited hypercalcemia, hyperphosphatemia, hypercalciuria, and impaired bone mineralization. Treatment of OVX rats with 1,24,25(OH)3D3 alone, on the other hand, only slightly increased serum calcium levels and did not impair bone mineralization. Furthermore, the inclusion of 1,24,25(OH)3D3 with 1,25(OH)2D3 partially antagonized the untoward effects of 1,25(OH)2D3 on bone mineralization.These data suggest that the actions of 1,24,25(OH)3D3 on bone metabolism might differ from that of 1,25(OH)2D3, and that 1,25(OH)2D3 and, particularly, 1,24,25(OH)3D3 may be potentially effective agents for the prophylaxis of postmenopausal osteoporosis.Zusammenfassung40 Fischer-344-Ratten (10 Wochen alt, 130 g KG) wurden entweder beidseitig ovariektomiert (OVX) oder scheinoperiert (SHAM). Die Ratten wurden in folgende Gruppen eingeteilt: SHAM; OVX; OVX + 15 ng 1α,25-Dihydroxyvitamin D3 [1,25(OH)2)D3]/Tier/Tag (d); OVX + 30 ng 1α,24R,25-Trihydroxyvitamin D3 [1,24,25(OH)3D3]/Tier/d; OVX + 15 ng 1,25(OH)2)D3/Tier/d + 30 ng 1,24,25(OH)3D3/ Tier/d. 4 Wochen post Operationem wurde mit der oralen Verabreichung der Vitamin-D-Metaboliten begonnen. Urin- und Blutproben wurden mehrfach während des Experiments entnommen. 21 Wochen post Operationem wurden alle Ratten getötet und die proximale Tibia sowie der erste Lendenwirbelkörper für eine statische histomorphometrische Auswertung unentkalkt eingebettet.Die Ovariektomie verursachte eine Abnahme der trabekulären Knochenmasse um 40% im Lendenwirbelkörper und um 69% in der Tibiametaphyse. Verglichen mit den scheinoperierten Tieren, ging der Knochenverlust bei OVX-Ratten mit mä\ig erhöhten biochemischen und histomorphometrischen Parametern der Knochenformation und -resorption einher. Die Behandlung der OVX-Ratten mit 1,25(OH)2)D3, 1,24,25(OH)3D3 oder der Metabolitkombination verhinderte die durch die Ovariektomie induzierte Osteopenie im trabekulären Knochen des Lendenwirbels und teilweise auch der Tibiametaphyse, wobei diese Wirkung durch eine Hemmung der Knochenresorption zustande kam. Die mit 1,25(OH)2)D3 allein oder in Kombination mit 1,24,25(OH)3D3 behandelten Ratten zeigten jedoch eine Hyperkalzämie, Hyperphosphatämie, Hyperkalzurie und eine gestörte Knochenmineralisation. Andererseits führte die Behandlung von OVX-Ratten mit 1,24,25(OH)3D3 allein nur zu einer leichten Zunahme des Serumkalziumspiegels und erzeugte keine Störung der Knochenmineralisation. Weiterhin wirkte 1,24,25(OH)3D3 in Kombination mit 1,25(OH)2)D3 den ungünstigen Effekten von 1,25(OH)2)D3 auf die Knochenmineralisation teilweise entgegen.Diese Ergebnisse deuten darauf hin, da\ sich die Wirkungen von 1,24,25(OH)3D3 auf den Knochenstoffwechsel möglicherweise von denen des 1,25(OH)2)D3 unterscheiden und da\ 1,25(OH)2)D3 und insbesondere 1,24,25(OH)3D3 eventuell auch für eine wirksame Prophylaxe der postmenopausalen Osteoporose geeignet wären.

Uptake and release of [I-14C]ascorbic acid and [I-14C]dehydro-ascorbic acid by leucocytes of guinea pigs

Abstract The leucocyte membrane was found to be permeable to both ascorbic acid and dehydroascorbic acid in either direction. Mean ratios of uptake of dehydroascorbic acid to ascorbic acid by leucocytes of normally fed guinea pigs (1.41 ± 0.16) and of vitamin C-deficient animals (1.91 ± 0.22) are given. No difference in uptake behaviour was observed using leucocytes of animals depleted of vitamin C for up to 16 days. However, ratios for uptake decreased rapidly in leucocytes of such animals being depleted for longer than 20 days, but this was most probably due to inanition and resulting metabolic disorders. After incubation with ascorbic acid, in both groups, only ascorbic acid was found in leucocytes and only ascorbic acid was released during re-incubation. After incubation with dehydroascorbic acid only ascorbic acid was found to be present in leucocyctes of the control group, whereas in the deficient group both, ascorbic acid and dehydroascorbic acid, were found and both compounds were released. After incubation with dehydroascorbic acid in the control group, mainly ascorbic acid was released.

Synergistic effects of vitamin D metabolites.

The vitamin D3 metabolites 1 alpha,24R,25- and 1 alpha,25S,26-trihydroxy vitamin D3 and their combinations with 1 alpha,25-dihydroxy vitamin D3 were tested for antirachitic activity in rats, chicken and Japanese quails. The trihydroxylated compounds were found to increase the activity of 1 alpha,25-dihydroxy vitamin D3. Since this synergistic effect is restricted to calcium absorption and bone formation while bone calcium mobilization is unchanged, the combined administration might improve calcium balance. These findings raise the possibility of a more efficient therapy of vitamin D-dependent diseases with limited amounts of 1 alpha,25-dihydroxy vitamin D3.

Der Einfluß von Vitamin C und Zink auf die durch Kupfer erhöhte Rückstandsbildung von Cadmium beim Schwein

ZusammenfassungIn der Schweinemast werden dem Futter Kupfermengen zugesetzt, die den Bedarf der Tiere weit übersteigen. Dadurch verbessern sich einerseits die Gewichtszunahmen, andererseits wird jedoch, wie wir in früheren Arbeiten zeigen konnten, in den Nieren, Lebern und im Muskel vermehrt das Schwermetall Cadmium retiniert. In einem Fütterungsversuch mit weiblichen und männlichen kastrierten Ferkeln wurde versucht, diese kupferinduzierte Cadmiumerhöhung (bei 175 mg Cu pro kg Futter) durch Zulage von Zink bzw. Vitamin C zu kompensieren. Während eine Zinkzulage von 100 bzw. 200 mg Zink pro kg Futter die Cadmiumbelastung von Niere und Leber nicht verringern konnte, reduzierte der Zusatz von 1 000 mg Vitamin C die erhöhten Cadmiumgehalte der Organe wieder auf Werte, wie sie bei niedrigem Kupferzusatz (35 mg Cu pro kg Futter) erhalten werden. Dieser positive Effekt von Vitamin C tritt aber nicht nur dann auf, wenn durch hohe Kupfergaben die Cadmiumretention angehoben wurde. Auch bei den Schweinen, die lediglich 35 mg Kupfer in der Diät erhielten, reduziert Vitamin C den Cadmiumgehalt in den Organen signifikant um 35 bis 40 %. Vitamin C liefert damit in jedem Fall einen Beitrag zur Qualitätsverbesserung von Nahrungsmitteln tierischen Ursprungs.SummaryIn commercial pig fattening, copper is added to the feed in amounts that greatly exceed the requirements of the animals. On the one hand, this improves weight gain, but on the other, as we were able to recently prove, the retention of the heavy metal cadmium rises in the kidney, in the liver and in muscle. In a feeding experiment with female and male castrated piglets, we tried to counter the copper-induced rise in cadmium (175 mg Cu/kg feed) by adding zinc or vitamin C to the diet. While addition of 100 or 200 mg zinc per kg of diet had no influence, the addition of 1 000 mg vitamin C reduced the elevated cadmium values in the kidneys and livers to values only determined with a low copper supplementation of 35 mg copper per kg of feed. This positive vitamin C effect not only occurs in cases of high copper supplementation (175 mg Cu/kg feed); when the pigs were given only 35 mg copper per kg of feed, vitamin C also reduced the cadmium content in the organs by 35 to 40 %. This indicates that vitamin C improves the quality of food gained from animals for human consumption in both conditions.In commercial pig fattening, copper is added to the feed in amounts that greatly exceed the requirements of the animals. On the one hand, this improves weight gain, but on the other, as we were able to recently prove, the retention of the heavy metal cadmium rises in the kidney, in the liver and in muscle. In a feeding experiment with female and male castrated piglets, we tried to counter the copper-induced rise in cadmium (175 mg Cu/kg feed) by adding zinc or vitamin C to the diet. While addition of 100 or 200 mg zinc per kg of diet had no influence, the addition of 1000 mg vitamin C reduced the elevated cadmium values in the kidneys and livers to values only determined with a low copper supplementation of 35 mg copper per kg of feed. This positive vitamin C effect not only occurs in cases of high copper supplementation (175 mg Cu/kg feed); when the pigs were given only 35 mg copper per kg of feed, vitamin C also reduced the cadmium content in the organs by 35 to 40%. This indicates that vitamin C improves the quality of food gained from animals for human consumption in both conditions.

Biological Activity of Fluorine-Substituted 1,25-Dihydroxyvitamin D3 in Rats, in Chicken and in Japanese Quails

The biological activity of two fluorinated analogs of 1,25(OH)2D3 was compared with 1,25(OH)2D3 in various vitamin D assays. The effect of 24,24-F2-1,25(OH)2D3 on plasma calcium, bone weight and duodenal calcium binding protein in chicken, on calcium excretion via egg shell in Japanese quails and on mobilization of calcium from the bone in rats was twice as high as the effect of the most potent naturally occurring vitamin D3 metabolite 1,25(OH)2D3. In contrast, 24R-F-1,25(OH)2D3 has less than 50% of the potency of 1,25(OH)2D3. Due to the wider therapeutic dosage range, this compound might be of clinical value.

Einflüsse verschiedener Vitamin-D-Metaboliten auf das Beinschwäche-Syndrom bei Mastputen

In two experiments the influence of vitamin D metabolites on leg weakness in turkeys belonging to the Big 6 line was studied. The metabolites were given orally or intravenously in different dosages. There are no differences in vitamin-D-dependent parameters between healthy turkeys and turkeys with leg weakness. Additional oral application of 1,25 (OH)2D3 in dosages of 2, 5 or 10 micrograms per animal day and of 400 micrograms 25 (OH)D3 per animal day had no influence on leg weakness. Even after intravenous application of 2 or 5 micrograms 1,25(OH)2D3 per animal day there were no changes concerning the degree of leg weakness nor were any signs of hypervitaminosis D observed (increase of serum calcium level or increase of the activity of duodenal calcium binding protein). Our results indicate that this form of leg weakness in turkeys is not connected to a disturbance of vitamin D metabolism.ZusammenfassungIn zwei Versuchen mit beinschwachen Truthähnen der Mastlinie „BIG 6“ wurde der Einfluß verschiedener Vitamin-D-Metaboliten nach oraler bzw. intravenöser Verabreichung untersucht. Zwischen kranken und gesunden Tieren wurden bei den Vitamin-D-abhängigen Parametern keine Unterschiede festgestellt. Zusätzliche orale Gaben mittels Schlundsonde von 1,25(OH)2D3 in einer Dosierung von 2, 5 bzw. 10 μg pro Tier und Tag sowie von 400 μg 25(OH)D3 pro Tier und Tag hatten keinen Einfluß auf die Erkrankung. Bei i.v. Applikation von 2 bzw. 5 μg 1,25(OH)2D3 pro Tier und Tag traten keinerlei Anzeichen einer Besserung des Gesundheitszustandes, aber auch keine Hinweise auf eine Hypervitaminose (Erhöhung des Serumcalciumspiegels bzw. Anstieg der Aktivität des Calcium bindenden Proteins) auf. Die untersuchte Form der Beinschwächeerkrankung bei Mastputen ist offensichtlich nicht mit einer Störung des Vitamin-D-Stoffwechsels verbunden.SummaryIn two experiments the influence of vitamin D metabolites on leg weakness in turkeys belonging to the Big 6 line was studied. The metabolites were given orally or intravenously in different dosages.There are no differences in vitamin-D-dependent parameters between healthy turkeys and turkeys with leg weakness. Additional oral application of 1,25 (OH)2D3 in dosages of 2, 5 or 10 μg per animal day and of 400 μg 25 (OH)D3 per animal day had no influence on leg weakness. Even after intravenous application of 2 or 5 μg 1,25(OH)2D3 per animal day there were no changes concerning the degree of leg weakness nor were any signs of hypervitaminosis D observed (increase of serum calcium level or increase of the activity of duodenal calcium binding protein). Our results indicate that this form of leg weakness in turkeys is not connected to a disturbance of vitamin D metabolism.

Die Bedeutung von Tiermodellen für den Fortschritt der Wissenschaft

ZusammenfassungVersuchstiere können als Modell für den Menschen herangezogen werden, wenn Analogien zwischen tierischen und menschlichen Funktionen bestehen. Deshalb kommt der Wahl von Spezies und Stamm bei der Entwicklung solcher Modelle eine besondere Bedeutung zu. Die Kenntnis der ernährungsphysiologischen Besonderheiten einer Spezies ist die Voraussetzung für die Herstellung vollwertiger Diäten. Oft sind Vorleistungen bereits in der Zuchtstation zu erbringen, um kurative Modelle überhaupt erst anwenden zu können. Nur wenn die hohen Anforderungen an die Standardisierung des tierexperimentellen Teiles einer Untersuchung erfüllt sind, können klinische und subklinische Symptome eindeutig zugeordnet werden. Mit empfindlichen biochemischen Reaktionen lassen sich sowohl Imbalanzen und Interaktionen von Nähr- und Wirkstoffen sowie Substitutionserfolge erfassen. Ebenso können die Resorption und der Stoffwechsel von Präparaten verfolgt werden.Negative Auswirkungen auf das Analysenergebnis sind bereits bei der Wahl des Narkotikums, der Entnahme und Lagerung von Organproben auszuschließen. Wegen ihrer Bedeutung für die Planung und Auswertung stellt auch die Biometrie einen integrierenden Bestandteil eines jeden Forschungsprojektes dar.Die am Ganztier erzielte wissenschaftliche Information kann weder mit isolierten Organen und Zellkulturen, noch mit Hilfe simulierender Computersysteme erreicht werden.Große Anstrengungen, auch unter Einbeziehung biotechnologischer Methoden, sind erforderlich, um die Tierzahlen weiterhin zu reduzieren und gleichzeitig die Aussagekraft der Experimente zu erhöhen. In jedem Fall jedoch müssen die wissenschaftlichen Zielsetzungen mit den ethischen Anliegen des Tierschutzes in Einklang gebracht werden.SummaryExperimental animals may serve as models for human beings, if analogies between animal and human functions exist. Therefore, the selection of species and strain plays an important role in the development of such models. Knowledge of the nutritional and physiological characteristics of a species is a prerequisite for the composition of complete diets. Often, preliminary work has to begin at the breeding farm in order to make use of such curative models possible. Only when the high requirements of standardization of experimental animals are met can clinical and subclinical symptoms be determined distinctly. By means of sensitive biochemical reactions, imbalances and interactions of nutritive and active ingredients, as well as successful substitutions, can be recorded. The study of absorption and metabolism of preparations is made possible by observing these reactions.However, negative influence on the results of analysis must be eliminated by correct selection of narcotics, and the proper excision and storage of organs. Because of its importance for the planning and evaluation of experiments, biometry is an integral part of every research project.The scientific information which must be gained from the whole experimental animal cannot be substituted by either isolated organs and cell cultures, or by means of computer simulation.A demanding effort, which includes biotechnological methods, is necessary to further reduce the number of experimental animals and, simultaneously, to enhance experimental evidence. In any case, all scientific aims must be in accordance with the ethical principles of the Society for the Prevention of Cruelty to Animals.

The Ovariectomized Rat: A Model for Postmenopausal Osteoporosis?

In the first 5 years following the menopause most women experience a phase of rapid bone loss accompanied by increased bone turnover [1,2]. It is well established that rats develop cancellous bone osteopenia in the appendicular and axial skeleton after ovariectomy [3, 4]. However, there are some major differences between rat and human bone physiology and it remains to be clarified whether the ovariectomized rat can serve as a model for postmenopausal osteoporosis.

Aufnahme und Verteilung von 14 C-Retinylacetat in Organe und Sinnesgewebe (Innenohr) des Meerschweinchens

ZusammenfassungEs wird über die Aufnahme und chemische Identifizierung von14C-Retinylacetat in das Innenohr des Meerschweinchens nach per oraler Verabreichung berichtet. Die Untersuchung wurde aus methodischen Gründen bei Vitamin-A-mangelernährten Tieren durchgeführt. Es findet sich eine zeitabhängige Verteilung in den Sinnesgeweben, die der anderer Organe gleicht. Die chemische Identifizierung zeigt, daß das als Retinylacetat verabreichte markierte Vitamin A in den membranösen Strukturen des Innenohres in Form des Retinylpalmitats zu finden ist. Dies mag ein Hinweis sein auf die Fähigkeit des Innenohrgewebes, die Transportform des Vitamins A, das Retinol, zu verestern und eventuell auch zu speichern.SummaryThe uptake and chemical identification of14C-retinyl acetate in the inner ear of the guinea-pig after oral administration is reported. For methodological reasons the experiment was carried out in vitamin A-deficient guinea-pigs. In the sensory tissues a time-dependent distribution was found similar to that in other organs. The chemical identification shows that the orally administered labeled retinyl acetate can be detected as retinyl palmitate in the membranous structures of the inner ear. This may be an indication for the ability of the inner ear tissues to esterize and probably store the transport form of vitamin A, retinol.