Proliferation of skeletal muscle satellite cells after castration and administration of testosterone propionate.

Abstract

Thirty-six neonatal pigs were randomly assigned to the following treatment groups: sham implanted gonadally intact males (B), sham-implanted castrated males (C), or castrated males implanted with testosterone propionate (C + TP). Four pigs from each group were sacrificed at 7, 14, or 21 days of age after a 6-hr continuous infusion of [3H]thymidine. Myofibers isolated from the triceps brachii were prepared for satellite cell enumeration by light microscope autoradiography. A developmental decline in labeled myofiber nuclei occurred in all groups, however, the greatest decline occurred in C (P less than 0.01). A treatment-by-age interaction was observed for percentage of labeled nuclei. Castration reduced total and labeled nuclei per millimeter myofiber (P less than 0.05), and C + TP had a higher percentage of labeled nuclei than C (2.8 vs 2.2%; P less than 0.05). Since triceps brachii muscles from 21 day B and C + TP were 120% (P less than 0.05) of C, the results indicate that postnatal growth of skeletal muscle is dependent on satellite cell mitotic activity and that testosterone enhances this activity in neonatal pigs.