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Collagen metabolism following corneal laceration in rabbits
Abstract:
We investigated the synthesis and degradation of collagen in lacerated rabbit corneas. The rate of collagen synthesis was measured by the incorporation and hydroxylation of [14C]proline up to 5 weeks after a penetrating laceration. Our results indicate that protein and collagen synthesis is initially reduced during the 24 h period after laceration and then increases in two phases. A moderate increase in protein and collagen synthesis occurs up to day 5 after laceration. Synthesis then decreases to a low level through the 10th day after injury. A second wave of increase in protein and collagen synthesis takes place reaching a new peak of approximately twice the activity as found in control corneas after 5 weeks of healing. Afterwards, the rate of protein and collagen synthesis declines and reaches the basal level after 7 weeks of healing. In a separate set of experiments, rabbit corneas were lacerated and allowed to heal for one or three weeks at which point 100 microCi of [14C]proline was injected into each anterior chamber. The corneas were excised 1 to 17 days later and subjected to collagen analysis. Our data indicates that the degradation of collagen synthesized by the cornea 1 week after laceration followed biphasic kinetics. In the first phase, the half-life of newly-synthesized collagen is 20 days, whereas it is approximately 4 days in the second phase. It is of particular interest that the accelerated degradation of the newly-synthesized [14C]collagen is concomitant with the increased rate of collagen synthesis during the wound healing process. The degradation of collagen synthesized 3 weeks after injury was slower and followed monophasic kinetics having a half-life of 14 days. The degradation of non-collagenous 14C-proteins follow a monophasic kinetics having a half-life of 6-7 days. Polyacrylamide gel electrophoresis of newly-synthesized collagen indicated that the collagen(I) and collagen(V) were the main collagenous components synthesized by the lacerated corneas.