EFFECTS OF AMINO-ACIDS ON THE ABSORPTION OF TRIVALENT CHROMIUM AND ITS RETENTION BY REGIONS OF THE RAT SMALL-INTESTINE

This study utilized the double perfusion technique to measure the effects of dietary amino acids on the absorption of trivalent chromium (Cr3+) and its retention by regions of the rat small intestine. A nutrient-rich tissue culture medium (TCM) with Cr3+ was perfused through the intestinal lumen as a test meal. Simultaneously, a modified Krebs-Ringer Bicarbonate buffer was perfused through the intestinal vasculature to replace the intestinal blood supply. In two experimental groups, amino acids were omitted from the test meal; one group received a buffered salt solution, the other a specially formulated TCM without amino acids. With no amino acids in the test meal, chromium transport into the vascular perfusate was less than 50% of control, while significantly more chromium (>200%) was retained by the intestinal mucosa. The retention of chromium was greatest in the proximal small intestine when amino acids were present; in their absence, the region of maximal retention shifted to the distal segment. We postulate that dietary amino acids provide ligands necessary for chromium uptake and its transport into the vasculature. The reasons for the regional specificity of the retained chromium are unknown but may reflect the active transport of ligands, such as amino acids or bile salts, that ligate chromium and other minerals. © 1990 Pergamon Press plc.