Submitted on October 28, 2008
Revised on April 10, 2009
Accepted on April 10, 2009
A Comparison of 2H2O and Phenylalanine Flooding Dose to Investigate Muscle Protein Synthesis with Acute Exercise in Rats
Heath G. Gasier1, Steven E Riechman1, Michael P. Wiggs1, Stephen F Previs2, and James D. Fluckey1*
1 Texas A&M University
2 Case Western Reserve University
* To whom correspondence should be addressed. E-mail: jfluckey{at}hlkn.tamu.edu.
The primary objective of this investigation was to determine if 2H2O and phenylalanine (F) flooding dose methods yield comparable fractional rates of protein synthesis (FSR) in skeletal muscle following a single bout of high intensity resistance exercise (RE). Sprague Dawley rats were assigned by body mass to either 4 h control (CON 4h, n = 6), 4 h resistance exercise (RE 4h, n = 6), 24 h control (CON 24h, n = 6) or 24 h resistance exercise (RE 24h, n = 6). The RE groups were operantly conditioned to engage in a single bout of high intensity, 'squat-like' RE. All rats were given an intraperitoneal injection of 99.9% 2H2O and provided 4.0% 2H2O drinking water for either 24 h (n = 12) or 4 h (n = 12) prior to receiving a flooding dose of L-[2,3,4,5,6-3H]F 16 h post RE. Neither method detected an effect of RE on FSR in the mixed gastrocnemius, plantaris or soleus muscle. Aside from the qualitative similarities between methods, the 4h 2H2O FSR measurements, when expressed %/h, were quantitatively greater than the 24h 2H2O and F flooding in all muscles, P<0.001; and the 24h 2H2O was greater than the F flooding in the mixed gastrocnemius and plantaris, P<0.05. In contrast, the actual % of newly synthesized protein was significantly higher in the 24 h 2H2O vs. 4 h 2H2O and F flooding dose groups, P<0.001. These results suggest that the methodologies provide 'qualitatively' similar results when studying a perturbation such as RE; however, due to potential quantitative differences between methods, the experimental question should determine what approach should be used.
