You need a break off of steroids. You need some time training without anabolic steroids to let new receptor site appear.
CHANGES IN TESTOSTERONE MUSCLE RECEPTORS - EFFECTS OF AN ANDROGEN TREATMENT ON PHYSICALLY TRAINED RATS
BRICOUT VA, GERMAIN PS, SERRURIER BD, GUEZENNEC CY
CELLULAR AND MOLECULAR BIOLOGY
40 (3): 291-294 MAY 1994
From results obtained in physiological investigations carried out on various tissues sensitive to androgens, it seems that the hormonal receptivity can reflect changes in the endocrine status and specific response of a tissue. The purpose of the present investigation was to test whether an androgen treatment could modify the receptivity to testosterone of the skeletal muscle and myocardium of endurance trained rats. The experiment extended over 8 weeks, and animals received injections of delayed testosterone heptylate every seven days. The myocardium and two skeletal muscles with opposed functions and typology were examined : the extensorum digitorum longus (EDL), and the soleus (SOL). Results obtained using techniques based upon the radio-competition principles provided information on the testosterone-receptor binding. The binding curves were plotted up to the saturating concentration of tritiated mibolerone, a synthetic androgen specific of androgen receptors. The quantity of receptors, calculated at the specific saturation plateau is expressed in fmol/mg protein. Results show that contractile muscular activity always increased the quantity of receptors whereas the steroid treatment decreased it. Thus for EDL and SOL of control trained rats the quantity of receptors was 0.78 and 0.82 fmol/mg protein, respectively, compared to 0.23 and 0.43 fmol/mg protein for sedentary testosterone-treated rats. The same ''contractile activity'' effect was observed on the myocardium but enhanced with values of 1.63 fmol/mg protein for control trained rats versus 0.30 fmol/mg protein for sedentary testosterone-treated rats. The receptivity to testosterone of the skeletal muscle and myocardium changes under the effect of an androgen treatment. The negative effect of the treatment is more patent on the heart and EDL, only or mostly consisting of fast twitch fibers, than on the SOL mostly consisting of slow twitch fibers