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  • 1
    Electronic Resource
    Electronic Resource
    1,25 dihydroxyvitamin d-induced inhibition of3H-25 hydroxyvitamin D production by the rachitic rat liverin vitro (1983)
    Springer
    Calcified tissue international 35 (1983), S. 461-464 
    Details
    ISSN: 1432-0827
    Keywords: Vitamin D metabolites ; Liver perfusion ; Liver homogenates ; 3H-25 hydroxyvitamin D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The effect of the vitamin D metabolites 1,25 dihydroxyvitamin D (100 pg/ml) and 25-hydroxyvitamin D (30 ng/ml) on hepatic production of3H-25 hydroxyvitamin D was investigated using rachitic liver perfusions and homogenates. 1,25 dihydroxyvitamin D inhibited hepatic3H-25 hydroxyvitamin D production in the liver perfusion (3.6 ± 0.4 vs 2.0 ± 0.5 pmol/liver,P〈0.05) and in liver homogenates (11.9 ± 0.6 vs 10.1 ± 0.4 pmol/g liver protein/3 h,P〈0.02). Inhibition was time and dose dependent. 25-hydroxyvitamin D inhibited production in liver homogenates (11.9 ± 0.6 vs 9.2 ± 0.1 pmol/g liver protein/3 h,P〈0.05) but not in the intact liver (3.6 ± 0.4 vs 3.4 ± 0.5 pmol/liver). The data indicate that 1,25 dihydroxyvitamin D is able to feedback regulate the production of its precursor, 25-hydroxyvitamin D. Although 25-hydroxyvitamin D also inhibits its own production in liver homogenates, it failed to alter total production in the intact liver, suggesting that this metabolite may require immediate access to the vitamin D 25-hydroxylase, located on the microsomes and mitochondria, to induce inhibition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02405077
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  • 2
    Electronic Resource
    Electronic Resource
    Dexamethasone stimulates osteogenic differentiation in vertebral and femoral bone marrow cell cultures: Comparison of IGF-I gene expression (1998)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 71 (1998), S. 382-391 
    Details
    ISSN: 0730-2312
    Keywords: dexamethasone ; bone marrow cell cultures ; IGF-I ; vertebrae ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Osteoblast-like cell cultures have been established from the marrow of adult rat vertebrae. We have simultaneously examined the response to dexamethasone (dex) treatment in cultures of young adult female vertebral and femoral marrow cells. Alkaline phosphatase (AP) activity was analyzed as well as the expression of mRNAs for osteocalcin (OC) and insulin-like growth factor I (IGF-I). The vertebral and femoral marrow cells were maintained for 7 days in primary culture with or without 10-8 M dex and then 6 days in secondary culture without dex or with 10-8 M or 10-7 M dex. All cells were examined on day 6 of secondary culture. Vertebral and femoral cultures each expressed the highest AP enzyme levels when grown with dex in primary culture (10-8 M) and secondary culture (10-7 M). Under all experimental conditions, vertebral cultures had lower AP enzyme activity than femoral cultures. When dex was omitted from secondary culture, OC gene expression was not detected in either vertebral or femoral passaged cells even if dex was present in primary culture. For dex conditions where OC was expressed, vertebral cultures had higher OC mRNA steady-state levels than femoral cultures. IGF-I gene expression was detected by Northern analysis in both vertebral and femoral secondary cultures. However, vertebral marrow cultures had much higher IGF-I mRNA levels compared to femoral cultures whether or not dex was present in primary culture. These findings demonstrate that dex supports the differentiation of both vertebral and femoral adult marrow osteogenic cells into osteoblasts. Our results support the hypothesis that osteoblastic marrow cultures differ depending upon which location in the skeleton they are from and that there are skeletal site-dependent differences in the insulin-like growth factor system components. J. Cell. Biochem. 71:382-391, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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