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Effects of clenbuterol administration on serum biochemical, histologic, and echocardiographic measurements of muscle injury in exercising horses

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  • 1 Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803.
  • | 2 Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803.
  • | 3 Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803.
  • | 4 Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803.
  • | 5 Equine Medication Surveillance Laboratory and the Laboratory for Drug Residue Studies, Department of Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803.
  • | 6 Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803.

Abstract

Objective—To determine the effects of clenbuterol, at a dosage of up to 3.2 μg/kg for 14 days, PO, on skeletal and cardiac muscle in healthy horses undergoing treadmill exercise.

Animals—12 healthy horses from 3 to 10 years old.

Procedures—Horses were randomly assigned to a control group (n = 6) or clenbuterol group (6) and received either saline (0.9% NaCl) solution or clenbuterol, PO, every 12 hours for 14 days. Horses were subjected to submaximal treadmill exercise daily during treatment. Muscle biopsy specimens were collected before and after treatment for determination of apoptosis. Echocardiographic measurements, serum clenbuterol and cardiac troponin I concentrations, and serum activities of creatine kinase and aspartate aminotransferase were measured before, during, and after treatment. Jugular venous blood samples were collected every 3 days during treatment. Echocardiography was repeated every 7 days after beginning treatment. Response variables were compared between treatment groups and across time periods.

Results—No significant effect of clenbuterol or exercise on response variables was found between treatment and control groups at any time point or within groups over time.

Conclusions and Clinical Relevance—Results did not reveal any adverse effects of treatment with an approved dose of clenbuterol on equine cardiac or skeletal muscle in the small number of horses tested.

Contributor Notes

Supported by a grant from the Equine Health Studies Program, School of Veterinary Medicine, Louisiana State University, and by Boehringer Ingelheim.

The authors thank Michael Kearney and Dr. Giselle Hosgood for assistance with statistical analysis.

Address correspondence to Dr. McConnico (mcconnico@vetmed.lsu.edu).