Regression of skeletal muscle of chicken wing after stretch-induced hypertrophy.

Regression of stretch-induced growth of the anterior latissimus dorsi muscle of the adult fowl was characterized by measuring weight, protein, RNA, DNA, and collagen content. After 7 days of hypertrophy the total amount of protein, RNA, DNA, and collagen increased by 59, 228, 82, and 23%, respectively, above the control contralateral muscle. On removal of the stimulus, regression back to normal weight and composition was complete in 13 days except for total DNA content, which was still elevated 21% after 29 days of regression. After 28 days of hypertrophy, the total amount of protein, RNA, DNA, and collagen were 100, 126, 96, and 27%, respectively, greater than controls. On removal of the stimulus regression was again rapid, but reversal of the hypertrophy was not complete 35 days later with the total protein and RNA still elevated by 16-22% and the total DNA 35% above control level. The increase in the total collagen during hypertrophy was attributable to about equal increases in both the epimysial collagen and the internal collagen of the muscle. The study shows that reversal of hypertrophy can occur almost as rapidly as the hypertrophy process. RNA and protein are lost more rapidly than DNA.