Transformations of Rat Skin Collagen With Special Reference to the Ageing Process

Abstract

Summary The formation of insoluble collagen in rat skin was studied both in vivo and in vitro in order to clarify the mechanism by which tropocollagen units are transformed into supermolecular structures, especially in relation to the ageing process. I. Suitable methods were developed for the fractionation and purification of soluble collagens (Fig. l), for the determination of the specific radioactivity of hydroxyproline in starch‐gel electrophoretic collagen fractions (Table IV, Fig. 2) and for the production of insoluble collagen in vitro (Fig. 12). II. The proportion of insoluble collagen was maximal in the skin of a newborn rat. The rapid growth period of the rat was characterized by an accumulation of collagen soluble in 0.5 M acetic acid at 4° (Fig. 3). The insoluble collagen was separated into two subfractions (designated ISC40 and ISCr). The proportion of collagen soluble in 0.5 M acetic acid upon heating at 40° (ISC40) increased with age (Figs. 4–5). ISCR could be brought into solution only after degradation of the collagen at temperatures above 60° (Fig. 5). Also the proportion of ISCR was maximal in the skin of a newborn rat (Fig. 4). The subfractions of insoluble collagen extracted by 0.5 M acetic acid at 40° from skins of 5‐day‐old rats consisted mainly of α‐ and β‐components. The proportions of β‐ and γ‐components were higher in corresponding fractions from skins of adult rats (Fig. 7). The ratio of hexmamine to hydroxyproline decreased rapidly in the insoluble collagen with advancing age (Table V). The content of free aldehyde groups was lower in the collagen of a lathyritic rat than in the collagen of a normal rat. The difference was largest in the a‐components (Table VII). The subfractions of insoluble collagen had different contents of aldehyde groups: ISC60°‐80° contained one acetaldehyde equivalent/TC less than ISC20°‐50° (Table VI). Incorporation studies indicated that insoluble collagen is formed faster in young than in adult rats (Table IX, Fig. 9). The half‐lives of 0.5 M NaC1‐soluble collagens from 6‐day‐old and 3‐month‐old rats were 27 and 73 hours, respectively (Fig. 10). The turnover of the α2‐component in 0.1 M acetic acid‐soluble collagen from a 6‐day‐old rat was faster than that of the α1‐component (Fig. 11). III. When skin slices labelled in vivo were incubated in vitro, the total and specific radioactivities of the hydroxyproline of the insoluble collagen increased during 8 hours (Table X, Fig. 12). The formation of insoluble collagen during incubation was augmented by (1) a rise in temperature of the incubation medium up to 37° (Fig. 13); (2) a decrease in the thickness of the slices to 0.3 mm (Table XI); and (3) the presence of calcium ions up to 3.0 mM concentration (Fig. 15). The 45Ca‐activity increased in the insoluble residue of skin when skin slices labelled in vivo were incubated in vitro (Table XIII). Metal cations influenced the formation of insoluble collagen in the following order of decreasing effectiveness (Table XIV and XV): Co2+ > Cu2+ > Cu+ > Au3+ = Ni2+ > Fe3+ >...

Cyclophosphamide Effect on Collagen Metabolism in Granulation Tissue, Skin, and Aorta of Rats

“…Immediately after removal, one granuloma and a sample of skin were cut with scissors in 0.5 M acetic acid, pH 3.4, at 4". Collagen was extractcd 3 times overnight and purified by 3 precipitations with 15 and 10 per cent sodium chloride followed by dialysis against 0.1 M disodium phosphate and water (HEIKKINEN 1968…”

The Effects of Cyclophosphamide and Azathioprine on Collagen in Skin and Granulation Tissue in Rats, and the Effects of Cyclophosphamide on Collagen in Human Skin

“…The other granuloma was immediately minced with scissors in 0.5 M acetic acid, pH 3.4 at 4". The acid soluble collagen was extracted 3 times overnight and purified by 3 precipitations with 15 % and 10 % sodium chloride followed by dialysis against 0.1 M disodium phosphate and water (HEIKKINEN 1968). The skin was shaved with an electrical hair cutter and 2 circular specimens with a diameter of 2.1 cm were taken Symmetrically from the lumbar regions, 1-2 cm apart from the skin wound in the sponge bearing rats.…”

Blue autofluorescence of human achilles tendon collagen in relation to aging.

“…Biochemical studies based on extraction procedures (2,7,8,12) indicated that crosslinking of collagen increases with age, with marked differences between animal species and organs. The importance of pyridinoline in the decreased hydration and increased stability and rigidity of old age collagen has been debated in the literature (3,14).…”