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Zinc Regulation of Skeletal Matrix Formation and Remodeling Activities in Growing Rats
Author(s) -
Hadley Kevin B.,
Hunt Janet R.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a626-d
Subject(s) - weanling , chemistry , medicine , zinc , endocrinology , alkaline phosphatase , femur , resorption , carbonic anhydrase , zymography , bone resorption , matrix metalloproteinase , biochemistry , enzyme , biology , surgery , organic chemistry
Zinc (Zn) deficiency causes abnormal skeletal development involving growth plate defects. Therefore, Zn regulation of bone matrix synthesis and resorption was investigated. Male weanling rats (n=6/group) were fed an AIN‐96G based diet with egg albumin, containing 2.5, 5, 7.5, 15, or 30 μg/g Zn as ZnCO 3 for 21d. Femur Zn and SLC39A2 (Zip2) mRNA levels were used as indicators of changes in bone Zn status. The Zn metalloenzymes, femur alkaline and tartrate resistant alkaline phosphatases (ALP and TRAP, respectively), carbonic anhydrase II (CAII), and matrix metalloproteinase (MMP) ‐2 and ‐9 activities from femoral‐head extracts were measured. Femur Zn (means ± SEM) increased directly (p ≤ 0.05) from 0.9 ± 0.1 to 4.2 ± 0.1 μmols Zn/g dry weight in rats fed 5 to 30 μg Zn/g diet. Changes in Zip‐2 gene expression were at least 10‐fold greater between 5 and 15 μg Zn/g diet, and then decreased to less than 50% at 30 μg/g, relative to rats fed 2.5μg/g. Average delta threshold cycle numbers were not significantly different, however. ALP and TRAP p‐nitrophenol (pNP) release activities increased (p≤0.05, 22 ± 9 to 61 ± 11 and 6 ± 1 to 16 ± 1 μmols pNP/mg, respectively) with dietary Zn from 7.5 to 30 μg/g diet. In contrast, zymography of MMP‐2 and ‐9 showed decreased activities (p ≤ 0.05, 26 ± 2 to 4 ± 2 and 9 ± 1 to 2 ± 1 units) from 2.5 to 5 μg Zn/g diet and then remained level, relative to 30 μg Zn/g values. CAII activity also remained nearly constant from 2.5 to 15 μg Zn/g, and then decreased from 21± 2 to 13 ± 3 munits/mg (p ≤ 0.05) at 30 μg Zn/g diet. These results indicate a dietary Zn requirement greater than 15μg/g for optimal bone mineralization potential in growing rats, and provide insight into osseous Zip‐2 regulation by Zn status.