The composition and characteristics of skin and muscle collagens from a freshwater catfish grown in biologically treated tannery effuent water

Abstract

The skin of catfish Gariepinus spp. reared in tannery effuent water (ETP) had an increased collagen content, decreased acid solubility and high carbohydrate association as compared with skin of normal fish. The skin collagen in either fish was composed of three distinct α chains with mobilities different from that of vertebrate type I α chains and two of these three chains were invariably present in the muscle collagen. The amino acid composition of ETP fish skin and muscle collagens were similar but were characterized by higher degrees of proline and lysine hydroxylation, indicating higher stability. Both the skin and muscle collagens had significantly high denaturation temperatures. Electron microscopy of in vitro reconstituted fibrils of skin and muscle collagens of ETP fish displayed defined periodicities of around 64 nm. This demonstrates that the polymorphism in skin collagen chains is not confined to marine fish. There was a close similarity in the composition of skin and muscle collagens and the ETP environment influences the solubility and stability of the skin collagen. It is hypothesized that the third chain may play a role in the anchorage of skin to muscle, as such chain composition is now evident in fish such as hake, cod and catfish where the musculature is strongly attached to the skin.