The intestinal zinc transport in aged rats

To determine if there are any age-related alterations in the intestinal zinc absorption that may contribute to zinc deficiency, we studied the zinc transport across the jejunal segments of 3-, 12- and 24-month-old Fisher 344 male rats using the Ussing chamber technique. We also evaluated the effect of 5 microM arachidonic acid in tissue bathing media. The zinc transport from mucosa to serosa in 24-month-old rats (55.0 +/- 3.5 nmol/h/cm2) was significantly greater than the transport in 12-month-old (30.1 +/- 6.3 nmol/h/cm2) and 3-month-old rats (41.0 +/- 5.2 nmol/h/cm2). There was no age-dependent differences in the zinc transport from the serosa to the mucosa. The addition of 5 microM arachidonic acid to the serosal side only resulted in a significant decrease in zinc transport rate from serosa to mucosa. The magnitude of change in the 24-month-old rats (36.0 +/- 3.9 vs. 26.5 +/- 3.2 nmol/h/cm2) was similar to the change seen in 12-month-old rats (34.5 +/- 4.6 vs. 20.1 +/- 3.5 nmol/h/cm2) and 3-month-old rats (34.5 +/- 4.6 vs. 26.1 +/- 3.9 nmol/h/cm2). The results indicate that intestinal zinc transport is increased in the aged rats, and that arachidonic acid or one of its metabolites may be important regulators of net zinc absorption through their effect on intestinal zinc secretion rates.