Effekte des ß‐adrenergen agonisten clenbuterol auf das wachstum der skelettmuskulatur von ratten

Abstract

The effects of clenbuterol (CB) on the weights of 6 hindleg muscles as well as on structural and biochemical characteristics of extensor digitorum longus muscle (EDL) were studied on Wistar rats. Different CB-doses (5 vs. 18 mg/kg diet) were tested and rats of different sex were used. The 12 days treatment accelerated the growth of the 6 hindleg muscles by 13 to 24% without predominant response of fast twitch or slow twitch muscles. The higher muscle weights were achieved by fibre hypertrophy as demonstrated by increased fibre diameters (+13 to +16%), and not by fibre multiplication. There was no evidence for a selective fibre hypertrophy of one of the metabolic fibre types. Fibre type composition shifted to the fast glycolytic fibres (FTG +0.7 to +4.9%-units). There were no significant differences in responses between the sexes of CB-doses. Clenbuterol decreased the nucleus/cytoplasm ratio, measured as nuclei number/mm2 fibre area, between 24 and 28% and the DNA/protein ratio by 17%. RNA content and RNA/DNA ratio were enhanced by 25 and 22%, respectively; the protein/RNA ratio remained unchanged. The results suggest that clenbuterol changes fibre type composition and stimulates fibre growth in a pretranslational stage of protein synthesis without addition of nuclei by satellite cell proliferation.

Molecular Regulation of Skeletal Muscle Growth and Organelle Biosynthesis: Practical Recommendations for Exercise Training

“…Furthermore, hypertrophic responses induced by various stimuli, from pharmacological to genetic interventions, were not always associated with increased myonuclear number. This was the case when hypertrophy was induced by genetic ablation of myostatin [220], treatment with the beta 2-adrenergic agonist clenbuterol [221] and overexpression of the serine/threonine kinase Akt [222] (Figure 4). Of note, lysine supplementation, known to stimulate muscle growth, is associated with mTORC1 pathway activation and SCs proliferation/differentiation in piglets [223,224].…”

Rapid analysis of three β‐agonist residues in food of animal origin by automated on‐line solid‐phase extraction coupled to liquid chromatography and tandem mass spectrometry

“…For the effect of repartitioning of carcass composition to decrease fat deposition, β‐agonists are often administered to food‐producing animals as growth promoters , which results in the presence of drug residues in meat. It has been proved that the consumption of meat containing β‐agonists can cause acute poisoning with symptoms such as headache, tachycardianausea, dizziness, and even death .…”