Stretch-induced growth in XXXX wing muscles: a new model of stretch hypertrophy.

@entity1347 @entity1573
A new model of stretch-induced growth is evaluated in four @entity1573 wing muscles stretched to different extents by a spring-loaded tubular assembly. Muscles grew in length and cross section in proportion to the extent to which they were stretched. Longitudinal growth was essentially completed within 1 wk, while muscles grew in cross section through at least 5 wk of stretch. The muscles were neither denervated nor immobilized, and muscle activity as measured by EMG was not increased. Oxidative enzyme activities increased substantially with stretch in the patagialis (PAT), a twitch muscle, but were relatively unchanged in the slow-tonic @entity1347 ( @entity1347 ). Stretch altered mitochondrial enzyme proportions in the PAT, but had little effect in the @entity1347 . Capillary density was unchanged with stretch in the PAT, but decreased in the @entity1347 . Capillary density was unchanged with stretch in the PAT, but decreased in the @entity1347 . Capillary-to-fiber ratio, however, increased in both muscles. We conclude that muscles grow and adapt enzymatically due to stretch, but that these responses are dissimilar in twitch and tonic muscles.
