| Summary: | The effect of zinc deficiency on the growth promoting effect of circulating IGF-I and the direct growth effect of GH on long bone growth were investigated. Food intake was decreased by lack of zinc in the diet. Tissue zinc content and plasma alkaline phosphatase activity were reduced by zinc deficiency. Systemic administration of human IGF-I increased the body weight, tail length and tibia epiphyseal cartilage width of control animals. This somatogenic action was impaired by zinc deficiency, as evidenced by continued weight loss, no increase in tail length and decreased tibial epiphyseal cartilage width of zinc deficient animals. Unilateral arterial infusion of GH increased the tibial epiphyseal width of the treated limb but not of the non-treated limb in control rats. However, no difference was found between the infused and the non-infused limb of zinc deficient animals, suggesting the occurrence of GH resistance on long bone growth in zinc deficiency. We conclude that zinc deficiency inhibits the growth promoting action of circulating IGF-I and the direct growth effect of GH on long bone growth.
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