COLLAGEN AND ELASTIN SYNTHESIS IN THE DEVELOPING CHICK AORTA

Thoracic aortas from 8- to 18-day embryonic chicks were incubated in vitro for 30 min with [3H]glycine and the newly synthesized, labeled proteins were subjected to polyacrylamide gel electrophoresis in sodium dodecyl sulfate. The gels were fractionated and the incorporation of label into procollagen (125,000 Mr) and tropoelastin (70,000 Mr) was estimated by summation of the radioactivity found in the appropriate regions of the gel. The analyses showed that at Day 8 approximately 14% of the incorporated [3H]glycine was found in procollagen and 22% in tropoelastin. In the following 6 days of development, there was a significant decline in the relative incorporation into procollagen and an increase into tropoelastin so that at Days 14-18 less than 10% of the label was found in collagen and 40% was now found in tropoelastin. Since glucocorticoids have been shown to alter the rate of synthesis of other proteins in the developing chick, 150 μg of hydrocortisone was injected into 8-day eggs and 24 h later the aortas were incubated and treated as described above. The pattern of protein synthesis exhibited by the hormone-treated aortas resembled that of 14- to 18-day embryos. Furthermore, incubation of 8-day aortas with 10-8 m hydrocortisone for 24 h produced a significant increase in the rate of elastin synthesis relative to that of other proteins. These results demonstrate that collagen and elastin synthesis vary during development of the chick aorta and they suggest that glucocorticoids may be involved in the control of their synthesis. © 1979.