Impairment of Bile Secretion Induced by Exhaustive Exercise in the Rat

Abstract

The effects of strenuous exercise on the mechanisms of bile formation were studied in rats. Animals (n = 8) were exercised to exhaustion in a rodent treadmill at a speed of 24m/min and a 12% slope. Hepatic glutathione concentration was significantly reduced (-40%) and liver malondialdehyde content significantly increased (+37%) when compared to sedentary controls (n = 6). Both serum alkaline phosphatase level and bile acid concentration were significantly higher in runners (+81% and +85%). Bile flow and the biliary secretion of bile acids were significantly reduced both in basal conditions and following an i.v. tauro-cholate infusion (0.5 µmol/min/100 g body wt). Biliary glutathione secretion was also significantly decreased following exercise. Cholestasis was caused by an impairment of both bile acid-dependent (BADF) and bile acid-independent fraction (BAIF) of bile flow (-25% and -29% respectively). Exercise caused a delay in the peak appearance time and a reduced biliary secretion of horseradish peroxidase, suggesting alterations in the functional integrity of the cytoskeleton. To test the protective effects of S-adenosyl-L-methionine (SAMe), rats received the drug for ten days at a daily dose of 8 mg/kg i.p. SAMe administration prevented hepatic glutathione depletion due to exercise, normalizing both bile flow and bile acid as well as glutathione secretion. Our results suggest that both glutathione depletion and alterations in fluidity and composition of hepatocyte membranes could contribute to the development of exercise-induced cholestasis.

Key words

Bile flow - bile acid - cholestasis - exercise - glutathione - S-adenosyl-L-methionine - rat