Therapeutic clenbuterol treatment does not alter Ca2+ sensitivity of permeabilized fast muscle fibres from exercise trained or untrained horses
JOURNAL OF MUSCLE RESEARCH AND CELL MOTILITY
Authors: Plant, DR; Kearns, CF; McKeever, KH; Lynch, GS
Abstract
Clenbuterol is a beta(2)-adrenoceptor agonist primarily used for treating bronchospasm and alleviating the symptoms of chronic obstructive pulmonary disease ( COPD) in the horse. In other species ( rats, mice, sheep, and cattle), chronic high doses of clenbuterol ( typically in the milligram per kilogram body weight range) has been shown to cause a muscle directed protein anabolic response. Clenbuterol can also modify muscle fibre composition and therefore potentially affect muscle function. This has implications for the performance of exercising horses being treated with therapeutic doses of clenbuterol ( typically in the microgram per kilogram body weight range) for bronchospasm or COPD. It is not known whether clenbuterol treatment affects muscle fibre function in horses. The purpose of this study was to examine the effects of a therapeutic dose of clenbuterol, with and without exercise, on the contractile activation characteristics of single membrane permeabilized fibres prepared from muscle biopsies. We tested the hypothesis that therapeutic treatment with clenbuterol would not affect muscle fibre function. Unfit Standardbred mares were treated for 8 weeks with; clenbuterol (2.4 mug/kg twice/day, 5 days/week) plus exercise ( 20 min at 50% (V) over dot O-2max 3 d/wk; CLENEX), clenbuterol only (CLEN), or exercise only ( EX). Muscle biopsies were taken from the gluteus medius muscle before and after treatment and stored in a glycerol-based solution to prepare permeabilized muscle fibres. The force - pCa relationship for fibres from CLEN horses was steeper ( P < 0.05) indicative of greater cooperative interactions within the thin. lament, however, fibre sensitivity to Ca2+ was unchanged. In contrast, the steepness of the force - pCa relationship was not changed in fibres from EX and CLENEX horses and Ca2+ sensitivity was also unaffected. Rigor force, activation in the absence of ATP, was not affected by any treatment indicating an approximately equivalent number of participating cross-bridges during activation. The results indicate that a therapeutic dose of clenbuterol to Standardbred horses does not affect the Ca2+-activated contractile characteristics of isolated muscle fibres.
Spectral surface plasmon resonance imaging for the detection of clenbuterol via three-dimensional immobilization of bioprobes
ANALYTICAL BIOCHEMISTRY
Authors: Yao, Manwen; Wu, Yichuan; Fang, Xiangyi; Yang, Yucong; Liu, Hongjun
Abstract
A method of immobilizing clenbuterol (CLEN) on the sensor chip for spectral surface plasmon resonance imaging (SPRi) was experimentally investigated. The bioprobes on the sensor chip were prepared by immobilizing bovine serum albumin (BSA) protein and conjugating CLEN molecules to BSA, which provides more active points and free orientations for specific binding. The calibration curve showed that the wavelength resonance shift decreased as the concentration of CLEN analyte increased, consistent with the inhibition principle. The limit of detection (LOD) was estimated to be 6.32 mu g/ml. This method proved to be highly specific, high throughput, label free, and operationally convenient. (C) 2015 Elsevier Inc. All rights reserved.