Reactive oxygen species (ROS) are natural products of oxidative phosphorylation. With increased muscular activity (particularly in older individuals), ROS are elevated to the point where they overpower intracellular buffers and protein damage and muscle dysfunction occur. Diaphragmatic fatigue constitutes a life threatening condition for patients suffering from disorders that increase the work load of the diaphragm. The applicants propose to determine the role of ROS in diaphragmatic fatigue in mature and senescent rats, the cellular processes and proteins affected, and the protective role of heat shock proteins. Three hypotheses will be tested: 1) The response to and recovery from fatiguing stimulation are significantly influenced by ROS; 2) Diaphragms from senescent animals are more susceptible to damage by ROS than diaphragms from mature animals and that this damage is primarily to the excitation-contraction coupling (ECC) process; 3) The protein of the 70 kDa heat shock protein family protects the diaphragm from the damaging effects of fatiguing stimulation.
Four specific aims will test these hypotheses. The first three will study intact diaphragm to provide correlative evidence. The last one will utilize single skinned fibers to explicitly test the hypotheses.
The aims will determine: 1) the time course of isometric force and levels of superoxide (O2- and important EC regulatory proteins (FKBP12, triadin, sorcin and junctin)) in perfused mature and senescent rat diaphragms subjected to fatiguing stimulation in the presence and absence of intracellular ROS scavengers; 2) the effects of L(+)-lactate (a product of fatigue that is reported to stimulate ROS production) on the response to fatiguing stimulation; 3) how whole body heat shock affects the response to fatiguing stimulation; 4) how the contractile proteins and Ca++ uptake and release properties of the sarcoplasmic reticulum are affected by fatiguing stimulation in single skinned fast- and slow-twitch diaphragm muscle fibers.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL060304-03
Application #
6056529
Study Section
Respiratory and Applied Physiology Study Section (RAP)
Project Start
1997-09-30
Project End
2002-02-28
Budget Start
1999-09-01
Budget End
2002-02-28
Support Year
3
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Case Western Reserve University
Department
Physiology
Type
Schools of Medicine
DUNS #
077758407
City
Cleveland
State
OH
Country
United States
Zip Code
44106
Brotto, Marco A P; Marrelli, Mauro T; Brotto, Leticia S et al. (2005) Functional and biochemical modifications in skeletal muscles from malarial mice. Exp Physiol 90:417-25
Nosek, Thomas M; Brotto, Marco A; Jin, Jian-Ping (2004) Troponin T isoforms alter the tolerance of transgenic mouse cardiac muscle to acidosis. Arch Biochem Biophys 430:178-84
Brotto, Marco A P; Nagaraj, Ramakrishnan Y; Brotto, Leticia S et al. (2004) Defective maintenance of intracellular Ca2+ homeostasis is linked to increased muscle fatigability in the MG29 null mice. Cell Res 14:373-8
de Paula Brotto, Marco Aurelio (2003) Temporal effects of stress by immobilization and sensitivity of the isolated rat pacemaker to isoproterenol: roles of corticosterone, neuronal uptake, and beta-adrenergic homogeneity. J Pharmacol Exp Ther 306:1152-8
Brotto, Marco A de Paula; Nosek, Thomas M; Kolbeck, Ralph C (2002) Influence of ageing on the fatigability of isolated mouse skeletal muscles from mature and aged mice. Exp Physiol 87:77-82
de Paula Brotto, M; van Leyen, S A; Brotto, L S et al. (2001) Hypoxia/fatigue-induced degradation of troponin I and troponin C: new insights into physiologic muscle fatigue. Pflugers Arch 442:738-44
Nagaraj, R Y; Nosek, C M; Brotto, M A et al. (2000) Increased susceptibility to fatigue of slow- and fast-twitch muscles from mice lacking the MG29 gene. Physiol Genomics 4:43-9
Nosek, T M; Brotto, M A; Essig, D A et al. (2000) Functional properties of skeletal muscle from transgenic animals with upregulated heat shock protein 70. Physiol Genomics 4:25-33
Brotto, M A; Andreatta-van Leyen, S; Nosek, C M et al. (2000) Hypoxia and fatigue-induced modification of function and proteins in intact and skinned murine diaphragm muscle. Pflugers Arch 440:727-34