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United States Department of Agriculture

Agricultural Research Service

Title: Silicon Deprivation Decreases Collagen Formation in Wounds and Bone, and Ornithine Transminase Enzyme Activity in Liver

Authors
item Seaborn, Carol - U OF WISC-MENOMONIE
item Nielsen, Forrest

Submitted to: Biological Trace Element Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 1, 2002
Publication Date: December 1, 2002
Citation: Seaborn, C.D., Nielsen, F.H. 2002. Silicon deprivation decreases collagen formation in wounds and bone, and ornithine transaminase enzyme activity in liver. Biological Trace Element Research. v.89.p.251-261.

Interpretive Summary: Silicon deficiency decreases the collagen concentration in bone of rats. Because collagen is needed for bone formation and wound healing, it seems reasonable that adequate dietary silicon intake is needed for these two processes. Thus, an experiment was performed to ascertain whether silicon deficiency would affect collagen-forming enzymes and collagen deposition in na model of wound healing. This model was the implantation of a polyvinyl sponge beneath the skin of a rat. The measurement of hydroxyproline, an amino acid formed from proline incorporated into collagen, was used to assess collagen formation and concentration. The total amount of collagen measured as hydroxyproline was lower in long bone and in the sponges taken from silicon-deficient rats than in silicon-adequate rats. Also, a lower amount of a dose of radioactive-labeled proline was converted into hydroxyproline (indicating lower collagen formation) in sponges taken from silicon-deficient rats than in sponges from silicon-adequate rats. Liver ornithine aminotransferase, an enzyme involved in collagen formation was significantly decreased by silicon deficiency. The findings are further evidence that silicon is needed for collagen formation, and thus is needed for normal bone formation and good wound healing.

Technical Abstract: Silicon (Si) deprivation decreases the collagen concentration in bone of nine-week old rats. Finding that Si deprivation also affects collagen at different stages in bone development, collagen-forming enzymes or collagen deposition in other tissues would have implications that Si is important for both wound healing and bone formation. Therefore, 42 rats in experiment tone and 24 rats in experiment two were fed a basal diet containing 2 ug or 2.6 ug Si/g, respectively, based on ground corn and casein, and supplemented with either 0 or 10 ug Si/g as sodium metasilicate. At three weeks, the femur was removed from 18 of the 42 rats in experiment one for hydroxyproline analysis. A polyvinyl sponge was implanted beneath the skin of the upper back of each of the 24 remaining rats. Sixteen hours before termination, and two weeks after the sponge had been implanted, each rat was given an oral dose of **14C-proline (1.8 uCi/100 g body wt). The total amount of hydroxyproline was significantly lower in tibia and sponges take from Si-deficient animals than Si-supplemented rats. DPMs of **14C-proline were significantly higher in sponge extracts from Si-deficient than Si- supplemented rats. Additional evidence of aberrations in proline metabolism with Si deprivation was that liver ornithine aminotransferase was significantly decreased in Si-deprived animals in experiment two. Findings of an increased accumulation of **14C-proline and decreased total hydroxyproline in implanted sponges, and decreased activity of a key enzyme in proline synthesis in Si-deprived animals indicates an aberration in the formation of collagen from proline in sites other than bone that is corrected by Si. This suggests that Si is a nutrient of concern in wound

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