Effect of Ammonia on in vitro Diaphragmatic Contractility, Fatigue and Recovery

• Published in: Respiration Vol. 69; no. 6; pp. 534 - 541
• Main Authors: Shanely, R. Andrew, Coast, J. Richard
• Format: Journal Article
• Language: English
• Published: Basel, Switzerland Karger 2002; S. Karger AG
• Subjects: Air breathing; Ammonia - pharmacology; Animals; Basic Science Investigations; Biological and medical sciences; Diaphragm - drug effects; Diaphragm - physiology; Female; Fundamental and applied biological sciences. Psychology; In Vitro Techniques; Muscle Contraction - drug effects; Muscle Fatigue - drug effects; Rats; Rats, Sprague-Dawley; Respiratory system: anatomy, metabolism, gas exchange, ventilatory mechanics, respiratory hemodynamics; Vertebrates: respiratory system; Metabolite; Exercise; Diaphragm; Rat; Rodentia; Contractility; Fatigue; Respiratory system; Ammonia; Vertebrata; Mammalia; Functional recovery; Animal; Physiology
• ISSN: 0025-7931; 1423-0356
• DOI: 10.1159/000066459

Background: Following strenuous exercise, in vivo diaphragmatic strength has been reported to decrease. This decrease has been suggested to result from an increase in metabolic by-products of intense exercise. Objective: We tested the hypothesis that physiological NH 3 concentrations adversely affect diaphragmatic contractility, fatigability, and recovery. Methods: Rat diaphragm strips were exposed to one of six experimental conditions (n = 6 per condition): Krebs-Ringer control solution, or the control solution with NH 3 added (in mM): 0.11, 2.5, 5.0, 10.0, or 14.0. Initial diaphragmatic contractility was assessed with the force-frequency response in the control solution. Following the first force-frequency response, the solution was replaced with one of the six solutions and a second force-frequency response was measured. Strips were then subjected to a short fatigue protocol and contractility was reassessed with a third force-frequency response. A longer fatigue protocol was then administered, followed by a 20-min recovery assessment period. Results: Ammonia significantly (p < 0.05) reduced diaphragmatic contractility, but only at concentrations of 5 mM or greater. Additionally, ammonia did not alter the rate of fatigue. Conclusions: This study suggests that physiological NH 3 concentrations do not adversely affect in vitro diaphragmatic contractility, fatigue, or recovery. These data are not consistent with diaphragmatic fatigue associated with exercise induced by arterial concentrations of NH 3 seen in humans, although further testing in situ or in vivo is needed.