In Vitro effects of zinc on markers of bone formation |
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Authors: | D Chen L C Waite W M Pierce |
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Institution: | (1) Department of Pharmacology & Toxicology, University of Louisville School of Medicine, 40292 Louisville, KY |
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Abstract: | Zinc deficiency is associated with a reduced rate of bone formation that can be corrected by supplementation of the deficient
diet with adequate amounts of zinc. This study was conducted to examine the effects of zinc on bone cell parameters associated
with bone formation.
Tibiae were removed from 19-d-old chicken embryos and incubated for 48 h in Dulbecco’s modified Eagle’s medium supplemented
with antibiotics, bovine serum albumin, and HEPES. The addition of zinc (25–200 Μg/dL) to tibial cultures resulted in a concentrationdependent
increase in alkaline phosphatase activity, an increase in the incorporation of proline into bone protein and an increase in
the posttranslational oxidation of proline to peptidyl hydroxyproline. These effects of zinc were all diminished by the addition
of 2,6-pyridine dicarboxylic acid, a chelator of zinc. The addition of either cycloheximide (10-5M), dactinomycin (10-8M), or hydroxyurea (10-3M) to tibial cultures also attenuated the effects of zinc.
The effect of zinc on bone cell DNA synthesis was measured by following the incorporation of3H-thymidine into DNA and by fluorometric measurement of cellular DNA content. These methods revealed that the addition of
zinc to cultured tibiae resulted in a concentration-dependent increase in tibial DNA content and synthesis rate. The magnitude
of the zinc-induced DNA increase was similar to the magnitude of the zinc-induced increases in alkaline phosphatase activity,
proline incorporation, and hydroxyproline synthesis. Normalization of these latter responses to tibial DNA content yield data
indicating that the effect of zinc on bone formation results from a zinc-induced increase in bone cell proliferation. |
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Keywords: | Bone formation zinc chick embryos cycloheximide dactinomycin hydroxyurea |
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