Introduction:
Intense exercise can cause cellular damage, resulting in activation of inflammatory and fibrotic reactions.

Aim:
The aim of the present study was to investigate how one session of intense exercise affected liver gene expression and concentrations of tumor necrosis factor α (TNF-α) and profibrotic transforming growth factor β (TGF-β) in untrained and trained rats.

Material and methods:
Here we investigated the impact of intense exercise on liver gene expression and concentrations of TNF-α and TGF-β in untrained and trained healthy rats (n = 30 each). The trained rats underwent 6 weeks of endurance training with increasing load. From each group, liver samples were collected before, immediately after, and 3 h after one session of intense exercise. Gene expression was evaluated with quantitative real-time polymerase chain reaction. Protein content was measured by enzyme immunoassay.

Results and discussion:
One session of intense exercise did not influence gene expression at any time point. In trained rats TNF-α and TGF-β was increased immediately after exercise (P = 0.011 and P = 0.009, respectively). The increase in TGF-β persisted 3 h post exercise (P = 0.045). In untrained rats the concentration of TNF-α did not change in any time point, while TGF-β was decreased both immediately and 3 h after intense exercise (P = 0.01 and P = 0.03, respectively).

Conclusions:
Intense exercise led to increased proinflammatory and profibrotic activity in the liver of trained rats.