title: Influence of acetaminophen consumption and exercise on Achilles tendon structural properties in male Wistar rats.
abstract: Chronic consumption of acetaminophen (APAP) during exercise training leads to a reduction in tendon stiffness and modulus compared with a placebo. We explored whether this effect could be due to a reduction in tendon collagen content or cross-linking. Ten-week-old male Wistar rats (n = 50) were divided into placebo or APAP groups and into sedentary or treadmill-exercised groups. APAP (200 mg/kg) or saline was administered once daily by oral gavage. Rats in the exercise groups ran on a treadmill 5 days per week for 8 wk with progression to 60 min per day, 20 m/min, and 8° incline. After 8 wk, lyophilized Achilles tendon samples were assayed for the collagen-specific amino acid hydroxyproline and cross-linking [hydroxylyslpyridinoline (HP)] content by high-performance liquid chromatrography. Collagen content was not influenced by exercise or APAP (P > 0.05). Compared with placebo, tendon water content was 7% (P = 0.006, main effect) lower in animals consuming APAP (placebo: 54.79 ± 0.8%, APAP: 50.89 ± 1.2%). HP in the Achilles tendon was 36% greater (sedentary: 141 ± 15, exercise: 204 ± 26 mmol/mol collagen) in the exercise-trained rats independent of drug treatment (P = 0.020, main effect). Independent of exercise, HP content was 33% lower (P = 0.032, main effect) in the animals consuming APAP (placebo: 195 ± 21, APAP: 140 ± 19 mmol/mol collagen). Our data suggests that chronic consumption of APAP results in a reduction in collagen cross-linking and a loss of tissue water independent of chronic exercise. This reduction in cross-linking and water content could contribute to the decrease in tendon stiffness noted in humans chronically consuming APAP.
authors.affiliation: Dept. of Physiology, Arizona College of Osteopathic Medicine, Midwestern Univ., Glendale, AZ 85308, USA. ccarro@midwestern.edu
authors.forename: Chad C
authors.initials: CC
authors.lastname: Carroll
authors.forename: Jamie A
authors.initials: JA
authors.lastname: Whitt
authors.forename: Amity
authors.initials: A
authors.lastname: Peterson
authors.forename: Brian S
authors.initials: BS
authors.lastname: Gump
authors.forename: Jamie
authors.initials: J
authors.lastname: Tedeschi
authors.forename: Tom L
authors.initials: TL
authors.lastname: Broderick
mesh_terms: D000082:Acetaminophen / Q000494:pharmacology*; D000125:Achilles Tendon / Q000187:drug effects* / Q000502:physiology*; D000818:Animals; D001696:Biomechanical Phenomena; D003094:Collagen / Q000502:physiology; D008297:Male; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000082:Acetaminophen; D003094:Collagen