Increase in skeletal muscle protein content by the ß-2 selective adrenergic agonist clenbuterol exacerbates hypoalbuminemia in rats fed a low-protein diet

Abstract

This investigation examined how the nutritional status of rats fed a low-protein diet was affected when the animals were treated with the ß-2 selective agonist clenbuterol (CL). Males (4 weeks old) from an inbred, specific-pathogen-free strain of hooded rats maintained at the Dunn Nutritional Laboratory were used in the experiments (N = 6 rats per group). CL treatment (Ventipulmin, Boehringer-Ingelheim Ltd., 3.2 mg/kg diet for 2 weeks) caused an exacerbation of the symptoms associated with protein deficiency in rats. Plasma albumin concentrations, already low in rats fed a low-protein diet (group A), were further reduced in CL rats (A = 25.05 ± 0.31 vs CL = 23.64 ± 0.30 g/l, P<0.05). Total liver protein decreased below the level seen in either pair-fed animals (group P) or animals with free access to the low-protein diet (A = 736.56 ± 26 vs CL = 535.41 ± 54 mg, P<0.05), whereas gastrocnemius muscle protein was higher than the values normally described for control (C) animals (C = 210.88 ± 3.2 vs CL = 227.14 ± 1.7 mg/g, P<0.05). Clenbuterol-treated rats also showed a reduction in growth when compared to P rats (P = 3.2 ± 1.1 vs CL = -10.2 ± 1.9 g, P<0.05). This was associated with a marked decrease in fat stores (P = 5.35 ± 0.81 vs CL = 2.02 ± 0.16 g, P<0.05). Brown adipose tissue (BAT) cytochrome oxidase activity, although slightly lower than in P rats (P = 469.96 ± 16.20 vs CL = 414.48 ± 11.32 U/BAT x kg body weight, P<0.05), was still much higher than in control rats (C = 159.55 ± 11.54 vs CL = 414.48 ± 11.32 U/BAT x kg body weight, P<0.05). The present findings support the hypothesis that an increased muscle protein content due to clenbuterol stimulation worsened amino acid availability to the liver and further reduced albumin synthesis causing exacerbation of hypoalbuminemia in rats fed a low-protein diet. Correspondence

Factors contributing to plasma TCO2and acid‐base state in Ontario Standardbred racehorses

“…Of the 11 horses with the lowest [TCO2] there was nothing remarkable about medications or feeding regimen, although 3 horses were on lasix and 3 on ventipulmin. Ventipulmin, a b2 adrenergic agonist, could contribute to lowering TCO2 by lowering pCO2 (Rose et al 1983); however, b2 adrenergic agonists have been shown to increase plasma volume expansion (Ewaldsson et al 2006) and also potentially induce hypoalbuminaemia (Sawaya and Lunn 1998), both of which would act to decrease [Atot]. Therefore, the ventipulmin is not likely responsible for the lowered TCO2 and increased [H + ] in these horses.…”

“…1983); however, β 2 adrenergic agonists have been shown to increase plasma volume expansion (Ewaldsson et al . 2006) and also potentially induce hypoalbuminaemia (Sawaya and Lunn 1998), both of which would act to decrease [A tot ]. Therefore, the ventipulmin is not likely responsible for the lowered TCO 2 and increased [H + ] in these horses.…”

Automated headspace solid-phase microextraction and on-fiber derivatization for the determination of clenbuterol in meat products by gas chromatography coupled to mass spectrometry

“…Clenbuterol (CB), which is a β 2 ‐agonist, is used pharmaceutically as a cough suppressant. In addition, the drug has been added illegally into the feedstuff of livestock to enhance animal growth and increase feeding efficiency by inhibiting fat synthesis, stimulating lipolysis, increasing protein synthesis, and carcass leanness . Long‐term or high‐dose use has been shown to illicit deleterious physiological side effects .…”