APStracts 3:0292C, 1996.

Myonuclear accretion is a major determinant of avian skeletal muscle growth. Mozdziak, P. E., E. Schultz, and R. G. Cassens. Department of Anatomy and Muscle Biology Laboratory, University of Wisconsin, Madison Wisconsin, 53706

APStracts 3:0292C, 1996.

The role of satellite cells and DNA unit size in determining skeletal muscle growth was studied after mitotic activity was inhibited in the left Pectoralis thoracicus of two-week-old tom turkeys using irradiation (25 Gy). Toms were killed and muscle weights were obtained 1 (n = 5), 4 (n = 6), 7 (n = 6), and 15 (n = 4) weeks after irradiation. Satellite cell mitotic activity and DNA unit size were determined using enzymatically isolated myofiber segments and image analysis. Irradiated and non-irradiated muscle weights increased (P &LT; 0.01) between all ages examined, but irradiated muscle weights were significantly (P &LT; 0.01) lower than non -irradiated muscle weights 4, 7, and 15 weeks after irradiation. Satellite cell mitotic activity was lower (P &LT; 0.01) in irradiated than in non-irradiated muscles 1 and 4 weeks post -irradiation, and resulted in a significant reduction (P &LT; 0.05) in the number of myofiber nuclei per mm at 4 and 7 weeks post -irradiation. Satellite cell mitotic activity was higher (P &LT; 0.05) in irradiated than in non-irradiated muscles at 7 weeks post -irradiation, but at 15 weeks post-irradiation, it had fallen to low levels in both muscles. There was no significant (P &GT; 0.10) difference in DNA unit size between muscles at any time, but there was an age-related increase (P &LT; 0.01) for both muscles. Irradiation reduced muscle growth through a transient reduction in myonuclear production at a critical time (3 to 6 weeks of age) in posthatch skeletal muscle development. The age-related increase in DNA unit size was not accelerated to compensate for the reduction in myonuclear accretion. Thus, it appears that muscle growth potential is governed mostly by myonuclear accretion, and to a lesser extent by DNA unit size.

Received 20 May 1996; accepted in final form 6 September 1996.
APS Manuscript Number C276-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 7 October 1996