Moderate long-term physical activity improves the age-related decline in bile formation and bile salt secretion in rats.

This study examined the effect of moderate long-term exercise, begun soon after weaning, on the age-related decline in bile formation and the secretory rate maximum (SRm) of taurocholate (TC), the major bile salt (BS) in rats. Eight-month-old sedentary (S) female Sprague-Dawley rats showed a significant decrease in basal and TC-stimulated bile formation when compared with 2.5-month-old S controls. As in younger rats, decreased biliary phospholipid (PL) output was associated with the TC SRm, but this change appeared much more rapidly in S animals, which also exhibited significant increased plasma lipids and higher TC concentrations in plasma and liver at the end of the TC infusion. Exercise significantly improved bile flow (BF), including the bile salt-dependent and -independent fractions under basal and TC-stimulated conditions in 8 month-old rats. Although all the biliary parameters evaluated were improved, maximal BF and PL secretion values were affected the most and were virtually not different from those obtained in younger S animals. Exercise also significantly lowered the age-related elevation of plasma PL. Thus, moderate long-term exercise exerts a beneficial effect on hepatobiliary function and the BS SRm, an effect that may be attributed in part to increased availability of a biliary PL pool previously implicated in regulation of the BS SRm.