Age-related alterations in duodenal calcium transport rate in rats

To determine the age-related alterations in intestinal calcium transport under in vitro controlled conditions, we studied the calcium transport across duodenal segments of prepubertal (2 months), young adult (6 months) and aged (26 months) Fisher 344 male rats using the Ussing chamber technique. We also evaluated the effect of 10(-11) M 1,25-dihydroxycholecalciferol [1,25-(OH)2D3] in tissue bathing media. The calcium transport rate from mucosa-to-serosa (Jms) and from serosa-to-mucosa (Jsm) in 26-month-old rats (33.5 +/- 6.6 nmol/h per cm2 and 25.4 +/- 3.1 nmol/h per cm2, respectively) were significantly larger than that in 6-month-old animals (18.1 +/- 2.6 nmol/h per cm2 and 17.7 +/- 1.7 nmol/h per cm2 respectively). The Jms (46.1 +/- 12.0 nmol/h per cm2) and Jsm (50.8 +/- 7.2 nmol/h per cm2) in 2-month-old rats were significantly larger than the respective rates measured in 6-month-old animals. The addition of 1,25-(OH)2D3 minimized the age-related differences in mucosal calcium transport but did not significantly stimulate Jms. The magnitude of change in 1,25-(OH)2D3-stimulated Jsm in 6-month-old rats (17.7 +/- 1.7 vs. 29.4 +/- 2.2 nmol/h per cm2) was similar to that seen in 26-month-old rats (25.4 +/- 3.1 vs. 47.5 +/- 4.5 nmol/h per cm2). The results indicate that the maturational reduction in intestinal calcium transport capacity is followed by increased calcium fluxes in senescence.