Alterations in the Cross-Links of Skin Collagen of Rats Treated With Biosynthetic Growth Hormone

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Abstract
The effect of biosynthetic human growth hormone (b-hGH) treatment on rat skin collagen was investigated. Groups of rats were injected with b-hGH 0.16, 1.10 and 8.33 mg/kg/day for 90 days. The weight gain of the rats treated with b-hGH 1.10 and 8.33 mg/kg/day was 13% and 82% higher, respectively, compared with that of the placebo control group. The extractability of the skin collagen was studied by extraction with phosphate buffered saline (pH 7.4), followed by acetic acid (0.5 M) and acetic acid with pepsin. The reducible collagen cross-links were measured after reduction of the cross-links by KB3H4, followed by acid hydrolysis and ion-exchange chromatography. Furthermore, patterns of cyanogen bromide peptides were studied by SDS-poly-acrylamide-gel-electrophoresis. Peptides bound together by stable cross-links and the relative amounts of collagen type I and collagen type III were measured. Treatment with b-hGH 8.33 mg/kg/day resulted in increased extractability of the skin collagen in acetic acid, increased relative amounts of reducible collagen cross-links and reduced amounts of high molecular weight cyanogen bromide cleaved peptides of the collagen. These alterations probably reflect an increased synthesis of skin collagen induced by the highest dose of b-hGH. The relative amounts of collagen type I and collagen type III of the skin were not influenced by the b-hGH treatment.