Development of a new training protocol to induce skeletal muscle hypertrophy in male rats – Analysis of combinatory effects of training and anabolic steroids

To understand molecular mechanisms of skeletal muscle hypertrophy, suitable animal models are sufficient. These models give us the opportunity to investigate the complex interaction of training and anabolic steroids as well as the identification of physiological and endocrine side effects due to their abuse. Therefore in this study we developed a treadmill based hypertrophy training protocol for rats with the aim to simulate the situation of human athletes abusing steroids as close as possible.
The Rats were trained on a treadmill for six weeks. Training started with a velocity of 12 m/min and was increased progressively up to 29 m/min during the following five weeks. The rats performed two training sessions per day for 10 minutes and maintained a training rhythm of 3 days training and one day rest. The whole training protocol was performed at a steep angle of 25°. Between the end of the training and the section two additional days of rest where included to exclude short time effects on the endocrine system. The 32 trained intact male rats (strain=Wistar), were allocated into four groups. Group 1 = sedentary control group (C), group 2 = trained Group (EX), Group 3 = sedentary control group treated with metandienone (Meta) and Group ¬4 = Trained + Meta (Meta/EX). Meta animals were treated with a dose of 5mg/kg/bw/d Meta diluted in 20% ethanol and 80% peanut oil via s.c. injection. After six weeks animals were sacrificed and the weight of the heart, liver, kidney, seminal vesicle, visceral fat, testis, tibia, prostate, m. levator ani, m. soleus and m. gastrocnemius was determined. In addition blood and tissue samples were collected and prepared for histological and molecular analysis.
In EX and Meta/Ex animals the weight of the heart, m. soleus and m. gastrocnemius was significantly increased. Interestingly in Ex and Meta/Ex animals also the weight of the m. levator ani which is not involved in locomotion and the tibia weight was increased. Here additive effects of training/ Meta treatment could be observed. The visceral fat mass was significantly decreased due to training and/or steroid stimulus. Treatment with the anabolic steroids affected the weight of reproductive organs like prostate, seminal vesicle and testis, and has toxic effects on the liver and kidneys.
In summary our data demonstrate that our training protocol simulates the situation of humans on resistance training abusing anabolic steroids very closely. Studies on molecular mechanisms involved in skeletal muscle hypertrophy as well as toxic and endocrine side effects of anabolic agents are under investigation.