Measurement of dermal collagen synthesis rate in vivo in humans

Accumulation of collagen produces organ dysfunction in many pathological conditions. We measured the fractional synthesis rate (FSR) of dermal collagen in five human volunteers from the increment of [¹³C]proline in detergent-soluble dermal collagen hydroxylated to hydroxyproline during a continuous infusion of L-[1-¹³C]proline. In these and eight other volunteers, we measured [¹³C]proline enrichment in skin aminoacyl-tRNA, skin tissue fluid amino acid, and plasma. The prolyl-[¹³C]tRNA enrichment was one-half that in tissue fluid proline and more than threefold less than in plasma. The FSR of dermal collagen was 0.076 ± 0.063%/h (mean ± SD), similar to previously reported rates for skeletal muscle contractile proteins and substantially slower than hepatically derived circulating proteins such as albumin or fibrinogen. We conclude that the FSR of human dermal collagen resembles that of other human proteins considered to display slow turnover. The current method for its measurement may be used to determine the regulation of collagen synthesis in other organs and disease states.