Effects of inhibiting DNA synthesis with hydroxyurea on stretch-induced skeletal muscle growth.

Growth of chicken patagialis muscle in response to passive stretch for 7 days was studied in the absence and presence of the DNA synthesis inhibitor hydroxyurea. In the absence of hydroxyurea, the DNA content and concentration of the stretched muscle increased 101% and 40%, respectively, relative to the unstretched contralateral control. Stretch-induced growth was characterized by large increases in muscle wet weight (56%), protein content (44%), RNA concentration (63%), cross-sectional area (67%), and mean fiber cross-sectional area (50%). In the presence of hydroxyurea, DNA content increased only 22% whereas DNA concentration decreased 11% in response to stretch. However, except for RNA concentration, which increased 84%, stretch-induced growth in the hydroxyurea-treated birds exhibited the same characteristics as those in the sham-treated animals. Therefore, the large increase in DNA content and concentration observed after 7 days of stretch-induced growth in the chicken patagialis muscle was not necessary for the growth to occur.