Anabolic steroids are widely used and have a long history in amateur and professional athletics, especially in disciplines profiting from hypertrophy effects. Not only their detection is an objective of recent research but also the understanding of their underlying mechanisms and overall influence on the cellular signalling cascades. Enhancement of performance based on muscular hypertrophy relies on numerous pathways and a concert of factors which together induce a positive adaption process. This study takes a close up look at selected influential genes and pathways in the process of regeneration, hypertrophy and myogenesis in an animal experimental design in rat.
Two key independent variables are applied through interventional treatments of the test subjects - exercise and application of the anabolic steroid Metandienone, both designed to depict the real life situation of a steroid abusing athlete regarding intensity and focus of training and dosage of drug application. As the regulational network for influencing the physical ability athleticism and hypertrophy is a complex web of pathways, numerous biological processes have to be examined. In this thesis these factors cover major mitogens and systemic elements like the Androgen Receptor, IGF-1 and Pax7, several players in the muscle related TGF$\beta$-pathway - the Activin receptor IIB, myostatin, follistatin, Smad3 and Smad7, the myogenic factors MyoD and Myogenin, structural proteins through the embryonic myosin heavy chain and factors of the immune system - Tumor Necrosis Factor $\alpha$, Interleukin 6 and Interleukin 10. These factors are examined by comparative real-time PCR method in rat gastrocnemius muscle, demonstrating the wide array of organismic response to intervention on mRNA level. Furthermore, promising and important factors embryonic myosin heavy chain and MyoD are analyzed on protein level through western blot analysis. Finally, a possible definite structural influence is examined by histological analysis of fat tissue and \textit