Kligman L H, Gebre M, Alper R, Kefalides N A
Department of Dermatology, University of Pennsylvania School of Medicine, Philadelphia 19104.
J Invest Dermatol. 1989 Aug;93(2):210-4. doi: 10.1111/1523-1747.ep12277573.
Early biochemical studies of ultraviolet (UV) irradiated human skin reported a loss of insoluble collagen with a concomitant increase in the soluble fraction. Recent work has described an early increase in type III collagen during chronic irradiation of hairless mice as determined by cyanogen bromide digests of whole skin. In order to understand the correlation of these events and those seen with histochemistry, in the present study we irradiated hairless mice for up to 24 weeks with approximately 4 minimal erythema doses (MEDs) of UVB thrice weekly with Westinghouse FS-40 bulbs. Skin samples were taken at 4-week intervals from irradiated and age-matched control mice. Collagen was isolated from other skin proteins by acid extraction, pepsin digestion, and salt precipitation. Estimates of types I and III collagen were made by interrupted polyacrylamide gel electrophoresis and densitometric scanning. Compared with unirradiated controls, there was a small increase in the ratio of type III to total collagen after 8 weeks of UV. There were no significant increases at later time points until after 24 weeks of radiation. Total collagen in normal mouse skin, determined by hydroxyproline content, remained constant over the 24 weeks, while UV radiation produced significant increases at 4, 8, 12, and 16 weeks, returning to control levels at week 20. There was no change in the degree of hydroxylation at any time point in either group. Thus, chronic UV exposure resulted in increased collagen synthesis until late in the course of irradiation. Because there is a lack of consistent change in the ratio of type III to total collagen, the early increases in collagen content may represent both types I and III, synthesized in relatively unchanging proportions.
早期对紫外线（UV）照射的人体皮肤进行的生化研究报告称，不溶性胶原蛋白减少，同时可溶性部分增加。最近的研究表明，通过对无毛小鼠全皮进行溴化氰消化测定，在慢性照射过程中III型胶原蛋白会早期增加。为了了解这些事件与组织化学所见事件之间的相关性，在本研究中，我们使用西屋FS - 40灯泡，每周三次用约4个最小红斑量（MED）的UVB照射无毛小鼠长达24周。从照射组和年龄匹配的对照小鼠中每隔4周采集皮肤样本。通过酸提取、胃蛋白酶消化和盐沉淀从其他皮肤蛋白中分离出胶原蛋白。通过间断聚丙烯酰胺凝胶电泳和光密度扫描对I型和III型胶原蛋白进行估计。与未照射的对照组相比，UV照射8周后III型胶原蛋白与总胶原蛋白的比例略有增加。在24周辐射之前的后期时间点没有显著增加。通过羟脯氨酸含量测定，正常小鼠皮肤中的总胶原蛋白在24周内保持恒定，而UV辐射在第4、8、第12和16周时显著增加，在第20周恢复到对照水平。两组在任何时间点的羟化程度均无变化。因此，慢性UV暴露导致胶原蛋白合成增加，直至照射后期。由于III型胶原蛋白与总胶原蛋白的比例缺乏一致变化，胶原蛋白含量的早期增加可能代表I型和III型胶原蛋白均以相对不变的比例合成。
