Testosterone injection stimulates net protein synthesis but not tissue amino acid transport

Abstract

Testosterone administration (T) increases lean body mass and muscle protein synthesis. We investigated the effects of short-term T on leg muscle protein kinetics and transport of selected amino acids by use of a model based on arteriovenous sampling and muscle biopsy. Fractional synthesis (FSR) and breakdown (FBR) rates of skeletal muscle protein were also directly calculated. Seven healthy men were studied before and 5 days after intramuscular injection of 200 mg of testosterone enanthate. Protein synthesis increased twofold after injection ( P < 0.05), whereas protein breakdown was unchanged. FSR and FBR calculations were in accordance, because FSR increased twofold ( P < 0.05) without a concomitant change in FBR. Net balance between synthesis and breakdown became more positive with both methodologies ( P< 0.05) and was not different from zero. T injection increased arteriovenous essential and nonessential nitrogen balance across the leg ( P < 0.05) in the fasted state, without increasing amino acid transport. Thus T administration leads to an increased net protein synthesis and reutilization of intracellular amino acids in skeletal muscle.

Effects of very short rest periods on testosterone to cortisol ratio during heavy resistance exercise in men

“…2,27 The role of acute hormonal responses is very important because anabolic hormones such as testosterone will increase protein synthesis in muscle cells. 28 Rest interval between sets in RE has a special important which is defined as the time period between the ends of training set and commence of the next set so that body condition of the individual approached to the physiological stance before the activity. Amount of rest between sets affects the metabolism, cardiovascular function, hormonal response, also number of repetition in subsequent sets.…”

Physiological elevation of endogenous hormones results in superior strength training adaptation

“…Consequently, the role of the acute hormone responses to exercise can theoretically be important because anabolic hormones, i.e. testosterone and GH, can increase protein synthesis in muscle cells (Fryburg and Barrett 1993;Ferrando et al 1998). Therefore, exercise-induced stimulation of the endocrine system may be a trigger for additive adaptation processes in skeletal muscle cells, leading to increased content of contractile proteins.…”

Androgen receptor expression during C2C12 skeletal muscle cell line differentiation

“…Strong evidence indicate that testosterone (T), the main circulating androgen secreted by testicular Leydig cells under pulsatile luteinizing hormone stimulation, increases muscle mass and strength, both under physiological and pathological conditions. Physiologic T replacement therapy in healthy young hypogonadal men is associated with significant gains in fat free mass, muscle size and maximal voluntary strength (Bhasin et al, 2000;Snyder et al, 2000;Wang et al, 2000) Furthermore, the effects of androgens in male body composition is established by the use of T supplementation in older men with low levels of circulating hormone, being associated with a significant increase in lean body mass and a reduction in fat mass (Ferrando et al, 1998;Moreley et al, 1993;Sih et al, 2006;Snyder et al, 1999;Tenover et al, 1992) . The improvement of maximal voluntary strength in men with low T concentrations, is also dependent by T replacement therapy (Bhasin et al, 1997) .…”