Increased ϵ(γ-glytamyl)lysine crosslinking associated with increased protein synthesis in the inner layers of healing rat skin wounds

Abstract

Three days after biopsy wounds were made in the dorsal skin of rats the animals were killed and explants of wounded and unwounded skin were incubated for 7 h with either [ 3H]glutamine or [ 3H]lysine. Both incubated and fresh control explants were then dissected into three layers which were homogenized, extracted, digested and then assayed for ϵ(γ-glutamyl)lysine. The concentration of ϵ(γ-glytamyl)lysine was greater in all three wounded layers than in the corresponding unwounded layers. The concentration in the wounded middle (dermal) layer and in the unwounded middle layer of younger rats was greater than in the unwounded outer (keratinized) layer, which has previously been shown to contain ϵ(γ-glutamyl)lysine crosslinks. The incorporation of label from both [ 3H]glutamine and [ 3H]lysine into buffer-insoluble protein of the middle and inner (muscle) layers was much greater in the wounded explants than in the unwounded. Except for [ 3H]lysine in the inner layer there was also an increase in the fraction of incorporated label which was converted to ϵ(γ-glytamyl)lysine. These results show that increased protein biosynthesis during repair in the wounded explants is associated with increased formation of ϵ(γ-glutamyl)lysine. In addition, they indicate that the crosslink is involved in some process in the middle and inner layers which is distinct from its known function in keratinization of the epidermis.