Extracellular ATP, ADP or adenosine stimulation induces gene expression in skeletal miotubes

Skeletal muscle activation induces a slow calcium signal which is associated with gene expression. It has been shown that the release of ATP from muscle cells participates in the signal transduction pathway that induces this response. However, the specific receptors involved are still unknown. The aim of this study was to gain a first insight into the receptors involved in this gene expression signaling pathway. Rat skeletal miotubes were incubated with specific receptors agonists (ATP, ADP, UTP, UDP and adenosine) at different concentrations. Thereafter, interleukin-6 (IL-6) and c-fos mRNAs were analyzed with the RT-PCR method to determine the gene expression response to different extracellular receptors activation. High ATP (all P2Y and P2X purinergic receptors subtypes) concentrations induced increases in the gene expression of both IL-6 and c-fos, while high ADP (P2Y1 receptor) concentrations only induced increases in IL-6 mRNA. Neither UTP (receptors P2Y2 and P2Y4) nor UDP (receptor P2Y6) induced gene expression. Stimulation with adenosine (specific adenosine receptors) instead, showed a time and concentration dependent gene expression response, increasing mRNA for both IL-6 and c-fos but under different conditions. Thus, the results show that P2Y1 and adenosine receptors activation leads to gene expression, suggesting the participation of these receptors in the slow calcium signaling pathway.

Key words: slow calcium signal, nucleotide receptors, interleukin-6, c-fos