Interactive effects of denervation and malnutrition on diaphragm structure and function

Michael I. Lewis, Thomas J. Lorusso, Wen-Zhi Zhan, and Gary C. Sieck Division of Pulmonary/Critical Care Medicine, Department of Medicine, Cedars-Sinai Medical Center Burns and Allen Research Institute, Cedars-Sinai Medical Center, University of California, Los Angeles School of Medicine, Los Angeles, California 90048; and Departments of Anesthesiology and Physiology and Biophysics, Mayo Clinic, Rochester, Minnesota 55905 Received 20 June 1995; accepted in final form 27 June 1996. Lewis, Michael I., Thomas J. Lorusso, Wen-Zhi Zhan, and Gary C. Sieck. Interactive effects of denervation and malnutrition on diaphragm structure and function. J. Appl. Physiol. 81(5): 2165-2172, 1996. The purpose of this study was to examine the interactive effects of unilateral denervation (DN) and prolonged malnutrition (MN) on the structure and function of the diaphragm muscle (Dia). Four groups of rats were studied: control (Con), MN, DN, and DN-MN. MN began 2 wk after DN and lasted 4 wk. In both the DN and DN-MN groups, the relative loss in Dia weight exceeded the relative change in body weight. Compared with the Con group, Dia specific force was reduced by ~40% in both the DN and DN-MN groups but was unaffected in the MN group. Dia fatigue resistance improved in all experimental groups but to a greater extent in the DN and DN-MN groups. In both the DN and DN-MN groups, ~50% of Dia fibers were classified as type IIc, whereas fiber type proportions did not change in the MN group. In the DN group, only type IIb/x fibers atrophied, whereas all fiber types atrophied in the MN and DN-MN groups. We conclude that in the DN-MN group the reduction in specific force combined with the reduction in total cross-sectional area of the muscle significantly curtails Dia force-generating capacity. diaphragm contractility; diaphragm fiber type proportions; diaphragm fiber cross-sectional area 0161-7567/96 $5.00 Copyright © 1996 the American Physiological Society