Differences in the
protein composition of fast- and slow-twitch muscle may be maintained by different rates of
protein turnover. We investigated
protein turnover rates in slow-twitch soleus and fast-twitch plantaris of male Wistar rats (
body weight 412 ± 69 g). Animals were assigned to four groups (n = 3, in each), including a control group (0 d) and three groups that received
deuterium oxide (D2O) for either 10 days, 20 days or 30 days. D2O administration was initiated by an
intraperitoneal injection of 20 μL of 99% D2O-saline per g
body weight, and maintained by provision of 4% (v/v) D2O in the
drinking water available ad libitum. Soluble
proteins from harvested muscles were analysed by liquid chromatography-tandem mass spectrometry and identified against the SwissProt database. The enrichment of D2O and rate constant (k) of
protein synthesis was calculated from the abundance of
peptide mass isotopomers. The fractional synthesis rate (FSR) of 44
proteins in soleus and 34
proteins in plantaris spanned from 0.58%/day (CO1A1:
Collagen alpha-1 chain) to 5.40%/day NDRG2 (N-myc downstream-regulated gene 2
protein). Eight out of 18
proteins identified in both muscles had a different FSR in soleus than in plantaris (p < 0.05).