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 [hydroxylys-lpyridinoline (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.
|Journal||American Journal of Physiology - Regulatory Integrative and Comparative Physiology|
|Publication status||Published - 15 Apr 2012|