Effect of oxidant challenge on contractile function of the aging rat diaphragm

John M. Lawler, Camala C. Cline, Zhe Hu, Richard J Coast

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Although controversial, growing evidence indicates that reactive oxygen species (ROS) alter contractions of skeletal muscle, including the diaphragm. However, the impact of ROS on contractility of the aging diaphragm is unknown. The xanthine oxidase (0.01 U/ml) system was used as an ROS generator, imposing an oxidant challenge. Contractile function [twitch tension; twitch time to peak tension; twitch one-half relaxation time; tension at 10 and 20 Hz; maximal tetanic tension (P(o)) at 100 Hz] of costal diaphragm fiber bundles from young (4 mo) and old (25 mo) Fischer 344 rats was examined in vitro before and after treatment with control Krebs solution [young control (YC) and old control (OC)], or with xanthine oxidase (XO; 0.01 U/ml) plus hypoxanthine (0.29 mg/ml) substrate [young XO treated (YXO) and old XO treated (OXO)]. Contractile function of fiber bundles was reassessed after oxidant challenge in an unfatigued state (Post-u) or 10 min after a fatiguing stimulation protocol (Post-f). Oxidant challenge in the unfatigued fiber bundles increased twitch tension and tension at 10 and 20 Hz in YXO, but not OXO, without increasing P(o). Conversely, XO significantly depressed fatigued diaphragm twitch and low-frequency tension in both OXO and YXO, compared with controls. P(o) was depressed Post-f in OXO but not YXO. Oxidant challenge also increased twitch one-half relaxation time of the fatigued diaphragm in both age groups. Furthermore, fiber bundles from old rats suffered greater fatigue during the stimulation protocol. We conclude that the response to oxidant challenge and increased contractile demand is impaired in the aging diaphragm.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume272
Issue number2 35-2
StatePublished - Feb 1997
Externally publishedYes

Fingerprint

Diaphragms
Diaphragm
Oxidants
Rats
Aging of materials
Reactive Oxygen Species
Fibers
Xanthine Oxidase
Relaxation time
Hypoxanthine
Inbred F344 Rats
Fatigue
Muscle
Skeletal Muscle
Age Groups
Fatigue of materials
Substrates

Keywords

  • fatigue
  • free radicals
  • skeletal muscle
  • xanthine oxidase

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Biochemistry
  • Physiology (medical)

Cite this

Effect of oxidant challenge on contractile function of the aging rat diaphragm. / Lawler, John M.; Cline, Camala C.; Hu, Zhe; Coast, Richard J.

In: American Journal of Physiology - Endocrinology and Metabolism, Vol. 272, No. 2 35-2, 02.1997.

Research output: Contribution to journalArticle

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