BACKGROUNDPhosphatidic acid (PA) is a diacyl-glycerophospholipid that acts as a signaling molecule in numerous cellular processes. Recently, PA has been proposed to stimulate skeletal muscle protein accretion, but mechanistic studies are lacking. Furthermore, it is unknown whether co-ingesting PA with other leucine-containing ingredients can enhance intramuscular anabolic signaling mechanisms. Thus, the purpose of this study was to examine if oral PA feeding acutely increases anabolic signaling markers and muscle protein synthesis (MPS) in gastrocnemius with and without whey protein concentrate (WPC).METHODSOvernight fasted male Wistar rats (~250 g) were randomly assigned to four groups: control (CON, n = 6-13), PA (29 mg; n = 8), WPC (197 mg; n = 8), or PA + WPC (n = 8). Three hours post-feeding, gastrocnemius muscle was removed for markers of Akt-mTOR signaling, gene expression patterns related to skeletal muscle mass regulation and metabolism, and MPS analysis via the SUnSET method.RESULTSCompared to CON rats, PA, WPC and PA + WPC resulted in a significant elevation in the phosphorylation of mTOR (Ser2481) and rps6 (Ser235/236) (p CONCLUSIONSOur results are the first in vivo evidence to demonstrate that PA tends to increases MPS 3 h post-feeding, though PA may delay WPC-mediated MPS kinetics within a 3 h post-feeding window.