Zinc deficiency inhibits the direct growth effect of growth hormone on the tibia of hypophysectomized rats.

The effect of zinc deficiency on the direct-growth effect of growth hormone (GH) on tibia growth in hypophysectomized rats was studied. There were three dietary groups. Zinc deficient (ZD) group (0.9 mg/kg diet), control (C) group (66 mg/kg diet) and zinc adequate pair fed (PF) group (66 mg zinc/kg diet). All rats in each group received local infusion of recombinant human-growth hormone (hGH) (1 microgram/d), except for half of the animals in the control group, which were sham-treated, receiving vehicle infusion only. The substances were infused continuously for 13 d by osmotic minipumps through a catheter implanted into the right femoral artery. Food intake was lower and body weight loss was greater in ZD, and PF animals compared with C animals (p < 0.001). Tissue-zinc concentration and plasma alkaline-phosphatase activity were decreased (p < 0.05) by dietary-zinc deficiency. GH infusion increased the tibial-epiphyseal width of the treated right limb, but not of the noninfused left limb in C and PF animals. However, in ZD rats, no difference was found between the infused and the noninfused limbs. These results demonstrate that zinc deficiency inhibits the direct-growth effect of GH on long-bone growth.