Fiber-type composition of nine rat muscles. II. Relationship to protein turnover

Abstract

Rates of protein synthesis in vivo and fiber-type composition were measured in nine limb muscles of female rats at ages ranging from weaning to 1 yr. In all muscles, there was a decline in protein synthesis with increasing age, mostly as a result of a fall in the RNA content. Rates of protein breakdown and growth were determined in six muscles and these also declined with age. Regression analysis of the data for all ages showed that protein synthesis was correlated with the content of slow oxidative fibers but not with the relative proportions of fast glycolytic to fast oxidative glycolytic fibers.

Endurance exercise with reduced muscle glycogen content influences substrate utilization and attenuates acute mTORC1- and autophagic signaling in human type I and type II muscle fibers

“…The phosphorylation of eEF2 Thr56 was considerably higher in type II than in type I fibers in resting muscle in agreement with previous studies [11, 50], suggesting a higher basal rate of protein synthesis in type I than in type II fibers [51]. A higher rate of protein synthesis in slow-twitch compared to fast-twitch muscle has previously also been reported in rodents [52, 53]. Whether a possible fiber-type specific difference in resting synthetic rate may influence the response to exercise with reduced availability of muscle glycogen is presently unknown.…”

Endurance exercise with reduced muscle glycogen content influences substrate utilization and attenuates acute mTORC1- and autophagic signaling in human type I and type II muscle fibers

“…The phosphorylation of eEF2 Thr56 was considerably higher in type II than in type I fibers in resting muscle in agreement with previous studies [11, 50], suggesting a higher basal rate of protein synthesis in type I than in type II fibers [51]. A higher rate of protein synthesis in slow-twitch compared to fast-twitch muscle has previously also been reported in rodents [52, 53]. Whether a possible fiber-type specific difference in resting synthetic rate may influence the response to exercise with reduced availability of muscle glycogen is presently unknown.…”

Protein synthesis rates in human muscles: neither anatomical location nor fibre‐type composition are major determinants

“…Qualitatively, our results are comparable with the observations made in other species, predominantly rodents (Laurent et al 1978;Bates & Millward, 1983;Kelly et al 1984;Garlick et al 1989;Lang et al 2003); but the extent to which protein synthesis rates varied between different human muscles was much less in our study than that in studies of animals. It has been speculated that fibre-type composition is responsible for the differences between muscles.…”

Age-Related Changes in Skeletal-Muscle Myosin Heavy-Chain Composition: Effect of Mechanical Loading

“…On the basis of CH in plantaris, it seems that skeletal muscles of young rats are more sensitive to continuous mechanical loading induced by gastrocnemius tenotomy. This might be caused by a more intensive muscle-protein synthesis rate in young animals (Garlick, Maltin, Baillie, Delday, & Grubb, 1989;Hasten et al, 2000). These findings are consistent with an earlier study in humans (Yarasheski, Zachwieja, & Bier, 1993) in which muscle-protein synthesis rate in young and elderly skeletal muscle was very sensitive to a high-resistance exercise-induced stimulus (Trappe et al, 2002).…”

Endurance exercise with reduced muscle glycogen content influences substrate utilization and attenuates acute mTORC1- and autophagic signaling in human type I and type II muscle fibers

“…The phosphorylation of eEF2 Thr56 was considerably higher in type II than in type I fibers in resting muscle in agreement with previous studies [11, 50], suggesting a higher basal rate of protein synthesis in type I than in type II fibers [51]. A higher rate of protein synthesis in slow-twitch compared to fast-twitch muscle has previously also been reported in rodents [52, 53]. Whether a possible fiber-type specific difference in resting synthetic rate may influence the response to exercise with reduced availability of muscle glycogen is presently unknown.…”

Protein synthesis rates in human muscles: neither anatomical location nor fibre‐type composition are major determinants

“…Qualitatively, our results are comparable with the observations made in other species, predominantly rodents (Laurent et al 1978;Bates & Millward, 1983;Kelly et al 1984;Garlick et al 1989;Lang et al 2003); but the extent to which protein synthesis rates varied between different human muscles was much less in our study than that in studies of animals. It has been speculated that fibre-type composition is responsible for the differences between muscles.…”

Age-Related Changes in Skeletal-Muscle Myosin Heavy-Chain Composition: Effect of Mechanical Loading

“…On the basis of CH in plantaris, it seems that skeletal muscles of young rats are more sensitive to continuous mechanical loading induced by gastrocnemius tenotomy. This might be caused by a more intensive muscle-protein synthesis rate in young animals (Garlick, Maltin, Baillie, Delday, & Grubb, 1989;Hasten et al, 2000). These findings are consistent with an earlier study in humans (Yarasheski, Zachwieja, & Bier, 1993) in which muscle-protein synthesis rate in young and elderly skeletal muscle was very sensitive to a high-resistance exercise-induced stimulus (Trappe et al, 2002).…”

Endurance exercise with reduced muscle glycogen content influences substrate utilization and attenuates acute mTORC1- and autophagic signaling in human type I and type II muscle fibers

“…The phosphorylation of eEF2 Thr56 was considerably higher in type II than in type I fibers in resting muscle in agreement with previous studies [11, 50], suggesting a higher basal rate of protein synthesis in type I than in type II fibers [51]. A higher rate of protein synthesis in slow-twitch compared to fast-twitch muscle has previously also been reported in rodents [52, 53]. Whether a possible fiber-type specific difference in resting synthetic rate may influence the response to exercise with reduced availability of muscle glycogen is presently unknown.…”

Protein synthesis rates in human muscles: neither anatomical location nor fibre‐type composition are major determinants

“…Qualitatively, our results are comparable with the observations made in other species, predominantly rodents (Laurent et al 1978;Bates & Millward, 1983;Kelly et al 1984;Garlick et al 1989;Lang et al 2003); but the extent to which protein synthesis rates varied between different human muscles was much less in our study than that in studies of animals. It has been speculated that fibre-type composition is responsible for the differences between muscles.…”

Age-Related Changes in Skeletal-Muscle Myosin Heavy-Chain Composition: Effect of Mechanical Loading

“…On the basis of CH in plantaris, it seems that skeletal muscles of young rats are more sensitive to continuous mechanical loading induced by gastrocnemius tenotomy. This might be caused by a more intensive muscle-protein synthesis rate in young animals (Garlick, Maltin, Baillie, Delday, & Grubb, 1989;Hasten et al, 2000). These findings are consistent with an earlier study in humans (Yarasheski, Zachwieja, & Bier, 1993) in which muscle-protein synthesis rate in young and elderly skeletal muscle was very sensitive to a high-resistance exercise-induced stimulus (Trappe et al, 2002).…”