Chronic clenbuterol treatment compromises force production without directly altering skeletal muscle contractile machinery

摘要

Clenbuterol is an adrenergic receptor agonist known to induce skeletal muscle hypertrophy and a shift towards faster muscle fibres, when administered chronically at high doses. However, when normalized to the muscle surface area, the increase in muscle force is no longer increased and even depressed. We show that muscle contraction and relaxation force kinetics were significantly reduced particularly in fast contracting muscles. We show that action potential-elicited Ca2+ transients were depressed in the fast contracting muscle. Our data show that chronic clenbuterol treatment reduces contractile efficiency, with altered contraction and relaxation kinetics, but without directly altering the contractile machinery. Lower Ca2+ release during contraction could partially explain these deleterious effects.