Studies on Collagen of Bovine Cornea

Abstract

Soluble collagen in bovine corneal stroma was determined by homogenizing and sequentially extracting the tissue with 0.45 m NaCl, pH 7.4, 0.5 m citrate buffer, pH 4.3, and 0.5 m acetic acid. Calf cornea contains about three times more soluble collagen than cow cornea. In both calf and cow, the salt-soluble fraction contains the most collagen. Though calf corneas contain citrate and acetic acid-soluble collagen fractions, they are reduced greatly in the cow cornea. Calf corneas were incubated with 3,4–3H-proline for estimation of collagen biosynthesis and the data show that cornea has the capacity for in vitro synthesis of collagen. The tissue utilized radioactive proline slightly better when stroma alone without the epithelium was used. The specific activity of collagen was high in the salt-soluble fraction and also in the dialyzed incubation medium (containing collagen and soluble protein leached from the corneas). With the in vitro system, radioactivity was detected in the insoluble fibrous collagen in the corneas. Chelating agents, antibiotics, and other metabolic inhibitors markedly inhibited biosynthesis of collagen and other proteins. The iron chelator, α, α’-dipyridyl, selectively inhibits biosynthesis of corneal collagen.