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4.
Toxicology ; 97(1-3): 191-7, 1995 Mar 31.
Artículo en Inglés | MEDLINE | ID: mdl-7716786

RESUMEN

To clarify whether hypercalcemia after injection of Pb to rats is due to biological bone resorption or physicochemical mineral dissolution, the effect of lead (Pb) on release of previously incorporated 45Ca in organ culture was investigated. Pb at 50 microM and above stimulated the release of 45Ca and hydroxyproline (Hyp). Pb did not stimulate 45Ca release from the bones inactivated by freezing and thawing. Eel calcitonin (ECT), bafilomycin A1 and scopadulcic acid B (SDB) inhibited Pb-stimulated 45Ca release. These results indicate that Pb-induced 45Ca release is due to osteoclastic bone resorption. Pb-stimulated bone resorption was inhibited by indomethacin and flurbiprofen. Pb stimulated the release of prostaglandin E2 (PGE2) from the bones into the media. There was significantly high correlation between 45Ca and PGE2 release. Pb-induced bone resorption was inferred to be mediated by PGE2. From these results, it was suggested that hypercalcemia after Pb injection might be caused by biological bone resorption.


Asunto(s)
Resorción Ósea/inducido químicamente , Plomo/toxicidad , Macrólidos , Animales , Antibacterianos/farmacología , Calcitonina/farmacología , Calcio/metabolismo , Dinoprostona/biosíntesis , Hidroxiprolina/metabolismo , Ratones , Técnicas de Cultivo de Órganos
5.
Calcif Tissue Int ; 56(1): 49-53, 1995 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-7796346

RESUMEN

Bone-resorbing activities of 24-epi-1 alpha-hydroxyvitamin D2 [24-epi-1 alpha(OH)D2], 24-epi-1 alpha,25-dihydroxyvitamin D2 [24-epi-1,25(OH)2D2], and 1 alpha,24S,25-trihydroxyvitamin D2 [1,24S,25(OH)3D2], which might be a metabolite of 24-epi-1,25(OH)2D2, were investigated. In an in vitro bone resorption test, the activity of 24-epi-1 alpha(OH)D2 was similar to that of 1 alpha-hydroxyvitamin D3 [1 alpha(OH)D3] at 10(-9) M-10(-6) M. The activity of 24-epi-1,25(OH)2D2 was weaker than that of 1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3] at 10(-11) M-10(-8) M. On the other hand, the activity of 1,24S,25(OH)3D2 was similar to that of 24-epi-1,25(OH)2D2 at 10(-11) M-10(-9) M. In the formation assay of osteoclast-like cells, the activity of 24-epi-1 alpha(OH)D2 was weaker than that of 1 alpha(OH)D3 at 10(-7) M. The activity of 24-epi-1,25(OH)2D2 was almost similar to that of 1,25(OH)2D3 at 10(-11) M-10(-7) M. The activity of 1,24S,25(OH)3D2 was significantly weaker than that of 24-epi-1,25(OH)2D2 at 10(-11) M-10(-9) M. In the two experiments, the potencies of 24-epi-1,25(OH)2D2 were about 100 times higher than those of 24-epi-1 alpha(OH)D2. In an in vivo/in vitro bone resorption test, the activity of 24-epi-1 alpha(OH)D2 was almost similar to those of 1 alpha(OH)D3 and 1,25(OH)2D3 and higher than those of 24-epi-1,25(OH)2D2 and 1,24S,25(OH)3D2. 24-epi-1 alpha-(OH)D2 and 1 alpha(OH)D3 were longer lasting than 24-epi-1,25(OH)2D2 and 1,25(OH)2D3 in this experiment.(ABSTRACT TRUNCATED AT 250 WORDS)


Asunto(s)
Resorción Ósea/inducido químicamente , Ergocalciferoles/farmacología , Animales , Resorción Ósea/metabolismo , Resorción Ósea/patología , Calcitriol/farmacología , Calcio/metabolismo , Hidroxicolecalciferoles/farmacología , Técnicas In Vitro , Ratones , Osteoclastos/efectos de los fármacos , Osteoclastos/patología , Osteoclastos/fisiología
6.
Phys Rev B Condens Matter ; 50(16): 12052-12056, 1994 Oct 15.
Artículo en Inglés | MEDLINE | ID: mdl-9975346
7.
Calcif Tissue Int ; 55(3): 190-7, 1994 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-7987732

RESUMEN

To determine the possibility that methyl substitution in 26- and 27-positions of 24R,25-dihydroxyvitamin D3 [24,25(OH)2D3] alters activities of the original compound, the effects of 24,25(OH)2D3 on calcium (Ca) regulating activity were compared with those of its methyl analog [24,25(OH)2(CH3)2D3] in addition to 1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3]. 24,25(OH)2D3 at 10(-6) M and 24,25(OH)2(CH3)2D3 at 10(-7) M and above significantly stimulated both bone resorption in neonatal mouse calvaria cultures and formation of osteoclast-like multinucleated cells (MNC) in mouse bone marrow cultures. A stimulative effect of 1,25(OH)2D3 on bone resorption and MNC formation was recognized in very low concentrations (10(-11) M and above). Although a potency of 24,25(OH)2(CH3)2D3 in stimulating bone calcium (Ca) mobilization and intestinal Ca transport was higher than that of 24,25(OH)2D3, the potencies of both compounds were similar to that of 1,25(OH)2D3 unlike in vitro experiments. As 1,24R,25-trihydroxy-26,27-dimethylvitamin D3 showed almost the same effect as 24,25(OH)2(CH3)2D3, the dihydroxy form is suggested to be hydroxylated at 1 alpha position and converted to trihydroxy form in vitamin D-deficient rats. From these results, methyl substitution in 26- and 27-position of 24,25(OH)2D3 was found to elevate Ca regulating activity of the original compound. In addition, it is suggested that the basis for a similarity in potency between 1,25(OH)2D3 and 24,25(OH)2D3 or its dimethyl analog in vitamin D-deficient rats is likely the result of 1 alpha-hydroxylation.


Asunto(s)
24,25-Dihidroxivitamina D 3/fisiología , Calcio/metabolismo , 24,25-Dihidroxivitamina D 3/análisis , 24,25-Dihidroxivitamina D 3/farmacología , Animales , Transporte Biológico/efectos de los fármacos , Transporte Biológico/fisiología , Resorción Ósea/fisiopatología , Calcio/farmacocinética , Células Cultivadas , Mucosa Intestinal/metabolismo , Intestinos/fisiología , Masculino , Osteoclastos/citología , Osteoclastos/metabolismo , Unión Proteica , Ratas , Ratas Wistar , Proteína de Unión a Vitamina D/metabolismo
8.
Calcif Tissue Int ; 54(2): 165-9, 1994 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-7516817

RESUMEN

To examine an effect of lead (Pb) on the process of osteoclast-like cell formation from its progenitors, we used a mouse bone marrow culture system in which osteoclast-like multinucleated cells (MNCs) were formed in response to bone-resorbing agents. In a 9-day culture period, Pb dose-dependently stimulated MNC formation over the concentration range 2-10 microM, whereas at 40 microM Pb, MNC formation declined. In an 11-day culture period, MNC formation reached a maximum at 5 microM Pb and decreased with increasing concentration of Pb at 10-40 microM. Pb-stimulated MNC formation was inhibited by both indomethacin and SC19220, an antagonist of prostaglandin E2 (PGE2) receptor. Pb stimulated the production of PGE2 in marrow cell cultures, suggesting that Pb-stimulated MNC formation is dependent on the production of PGE2. 3-Isobutyl-1-methylxanthine potentiated Pb-stimulated MNC formation and 2',5'-dideoxyadenosine, an inhibitor of adenylate cyclase, inhibited it. A calcium ionophore A23187 increased Pb-induced MNC formation and verapamil, a calcium channel blocker, depressed it. It is possible that a PGE2-induced increase in the levels of cyclic adenosine 3',5'-monophosphate (cAMP) and calcium ions in marrow cells is involved in Pb-induced MNC formation. Pb and parathyroid hormone showed a synergistic stimulation on MNC formation. From these results, Pb is thought to induce osteoclast-like cell formation by a mechanism involving PGE2 which increases the intracellular levels of cAMP and calcium ions.


Asunto(s)
Células de la Médula Ósea , Plomo/farmacología , Osteoclastos/citología , 1-Metil-3-Isobutilxantina/farmacología , Animales , Médula Ósea/metabolismo , Médula Ósea/fisiología , Calcimicina/farmacología , Calcitonina/farmacología , Diferenciación Celular/efectos de los fármacos , Diferenciación Celular/fisiología , Núcleo Celular/ultraestructura , Células Cultivadas , AMP Cíclico/análisis , AMP Cíclico/metabolismo , Ácido Dibenzo(b,f)(1,4)oxazepina-10(11H)-carboxílico, 8-cloro-, 2-acetilhidrazida/farmacología , Didesoxiadenosina/farmacología , Dinoprostona/metabolismo , Indometacina/farmacología , Masculino , Ratones , Ratones Endogámicos , Osteoclastos/metabolismo , Osteoclastos/ultraestructura , Hormona Paratiroidea/farmacología , Verapamilo/farmacología
9.
Calcif Tissue Int ; 53(5): 318-23, 1993 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-8287319

RESUMEN

Two fluoro analogs of 1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3], 24a-homo-24,24-difluoro-1 alpha,25-dihydroxyvitamin D3 [24aF2-homo-1,25(OH)2D3], and 26,27-dimethyl-24,24-difluoro-1 alpha,25-dihydroxyvitamin D3 [24F2-1,25(OH)2(Me)2D3] were examined for calcium (Ca)-regulating activity. The objective of the present study was to determine whether or not fluoro substitution at 24-position would alter activities of the original compounds, that is, 26,27-dimethyl 1 alpha,25-dihydroxyvitamin. D3[1,25(OH)2(Me)2D3] and 24-homo-1 alpha,25-dihydroxyvitamin D3 [24homo-1,25(OH)2D3], respectively. The relative activities of 24aF2-homo-1,25(OH)2D3, 24F2-1,25(OH)2(Me)2D3, and 1,25(OH)2D3 in competing with 1,25(OH)2D3 for binding to chick intestinal cytosol receptor were 0.28:0.5:1.0. The relative potencies of the same series of compounds in competition for the vitamin D-deficient rat serum binding sites were 0.04:0.15:1. Bone-resorbing activities of two fluoro analogs in cultures of neonatal mouse parietal bones were more potent than that of 1,25(OH)2D3. Similar results were recognized in stimulating activities of osteoclast-like cell formation. Responses of two fluoro analogs to intestinal Ca absorption were similar to that of 1,25(OH)2D3. The potencies of 1,25(OH)2D3 and its fluoro analogs in bone Ca mobilization were the highest with 1,25(OH)2D3, followed by 24F2-1,25(OH)2(Me)2D3 and 24aF2-homo-1,25(OH)2D3, in that order. From these results and the data of Paulson et al., fluoro substitution in 24-position of 1,25(OH)2D3 apparently does not alter their activities,hence, the fluoro substitution at 24-position of 1,25(OH)2D3 and the elongation of side chain of 1,25(OH)2D3 may not intensify Ca-regulating activity.


Asunto(s)
Calcitriol/análogos & derivados , Calcio/fisiología , Animales , Transporte Biológico/fisiología , Enfermedades Óseas Metabólicas/prevención & control , Resorción Ósea/fisiopatología , Huesos/metabolismo , Calcitriol/metabolismo , Calcio/metabolismo , Pollos , Mucosa Intestinal/metabolismo , Masculino , Ratones , Ratones Endogámicos , Estructura Molecular , Osteoclastos/citología , Ratas , Ratas Wistar , Receptores de Calcitriol/metabolismo , Relación Estructura-Actividad , Proteína de Unión a Vitamina D/metabolismo
10.
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