title: External anal sphincter fatigue is not improved by N-acetylcysteine in an animal model.
abstract: Oxidative stress is associated with skeletal muscle fatigue. This study tests the hypotheses that N-acetylcysteine (NAC) reduces fatigue and accelerates recovery of the rat external anal sphincter (EAS). Fifteen female Wistar rats were killed humanely. The EAS was mounted as a ring preparation and electrically stimulated with 50 Hz trains of 200 ms in duration every 4 s for three and a half minutes. Three groups were analysed: a control group (n = 5), a group pretreated with NAC (10(-4) mol L(-1); n = 5) and a group pretreated with NAC (10(-3) mol L(-1); n = 5). A novel fatigue index was formulated and was compared to a conventional method of expressing fatigue. There was no significant difference at concentrations of NAC (10(-4) mol L(-1); P > 0.05). At high concentrations of NAC (10(-3) mol L(-1)) there was a significant depression in peak twitch amplitude before fatigue (P = 0.04). N-acetylcysteine in both concentrations used, did not alter fatigue or recovery of the rat EAS. There was a significant positive correlation between the two methods of expressing fatigue but the conventional method produced a higher fatigue index (22.4% on average). N-acetylcysteine does not ameliorate fatigue or accelerate recovery of the EAS and may not be a useful medical therapy for faecal incontinence.
authors: Department of Surgery, Mater Misericordiae University Hospital, Dublin, Ireland.
authors: C F
authors: CF
authors: Healy
authors: C
authors: C
authors: McMorrow
authors: C
authors: C
authors: O'Herlihy
authors: P R
authors: PR
authors: O'Connell
authors: J F X
authors: JF
authors: Jones
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology* / Q000627:therapeutic use; D001003:Anal Canal / Q000187:drug effects* / Q000502:physiology*; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology / Q000627:therapeutic use; D005242:Fecal Incontinence / Q000503:physiopathology / Q000517:prevention & control; D005260:Female; D066298:In Vitro Techniques; D023421:Models, Animal; D018763:Muscle Fatigue / Q000187:drug effects* / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000975:Antioxidants; D000111:Acetylcysteine