Exercise and glucocorticoid-induced diaphragmatic myopathy.

Abstract

We tested the hypothesis that a chronically active muscle, such as the rat diaphragm, would be more resistant to glucocorticoid-induced myopathy than a less active locomotor skeletal muscle (plantaris). Furthermore, we sought to determine whether endurance exercise could antagonize the glucocorticoid-induced atrophy in the diaphragm. Rats were assigned to one of seven experimental groups (n = 10 per group) and injected daily over a 10-day period with either a sham solution or prednisolone acetate: group 1: control; sedentary and sham injected; group 2: control; exercise trained and sham injected; group 3; sedentary; prednisolone (0.5 mg.kg-1 x day-1); group 4: sedentary; prednisolone (1.0 mg.kg-1 x day-1); group 5: sedentary; prednisolone (2.0 mg.kg-1 x day-1); group 6: sedentary; prednisolone (5.0 mg.kg-1 x day-1); group 7: exercise trained; prednisolone (5.0 mg.kg-1 x day-1). Slope differences in the dose-response curves suggest that prednisolone-induced muscle atrophy in the plantaris was more severe than that in the diaphragm. Furthermore, high doses of prednisolone resulted in a differential effect on muscle bioenergetic enzyme activities in the plantaris and diaphragm. Prednisolone treatment (> or = 2 mg.kg-1 x day-1) resulted in a significant reduction in phosphofructokinase activity (expressed as microM substrate.min-1 x mg protein-1) and an increase in 3-hydroxyacyl-CoA dehydrogenase activity in the plantaris muscle. In contrast, prednisolone treatment did not influence phosphofructokinase activity (P > 0.05) in the diaphragm but decreased (P < 0.05) relative citrate synthase activity. Finally, 90 min daily of endurance exercise did not antagonize prednisolone-induced myopathy in either the diaphragm or the plantaris.

• Authors: F K Lieu, S K Powers, R A Herb, D Criswell, D Martin, C Wood, W Stainsby, C L Chen
• Journal: Journal of applied physiology (Bethesda, Md. : 1985) (J Appl Physiol (1985)) Vol. 75 Issue 2 Pg. 763-71 (Aug 1993) ISSN: 8750-7587 [Print] United States
• PMID: 8226480 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Muscle Proteins
• Prednisolone

Topics

• Adrenal Glands (pathology)
• Animals
• Atrophy (pathology)
• Body Water (metabolism)
• Body Weight (physiology)
• Diaphragm (enzymology, physiopathology)
• Female
• Muscle Proteins (metabolism)
• Muscles (pathology, physiopathology)
• Muscular Diseases (chemically induced, enzymology, physiopathology)
• Myofibrils (metabolism, ultrastructure)
• Organ Size (physiology)
• Physical Conditioning, Animal
• Prednisolone
• Rats
• Rats, Sprague-Dawley
• Respiratory Muscles (pathology, physiopathology)
• Sarcoplasmic Reticulum (metabolism)