Programmed synthesis of collagen during postembryonic development of the nematode Panagrellus silusiae

Abstract

The relative rate of collagen synthesis in the free-living nematode Panagrellus silusiae during postembryonic development was found to be discontinuous by measuring either the incorporation of tritium into material extracted as collagen or the amount of collagen-bound tritiated proline and hydroxyproline after 2-hr incubations of whole worms with [ 3H]proline. A peak of collagen production preceded each of the three molts that were examined. Moreover, protocollagen prolyl hydroxylase activity during each intermolt period paralleled the pattern of collagen synthesis. On the other hand, a triphasic pattern was not observed when noncollagenous proteins were labeled with either [ 3H]tryptophan or [ 3H]leucine. In addition, the level of soluble radioactive proline that accumulates in whole organisms after 2-hr incubation periods did not fluctuate appreciably during postembryonic development. The mean ratio of hydroxy-proline to proline in a number of collagen samples extracted at various times during the maturation phase was 0.113 ± 0.040. Pulse and chase experiments with [ 3H]proline indicated that most of the collagen synthesized during a peak period is lost after the second ecdysis following the labeling interval. In contrast, a considerable proportion of the collagen synthesized during nonpeak periods is retained throughout the postembryonic period. It is postulated that the modulated pattern of collagen biosynthesis in Panagrellus reflects, for the most part, a quantitative regulation of the production of cuticular collagen during postembryonic development.