Intestinal Absorption of Manganese in Experimental Malnutrition

Abstract

We investigated possible changes in mechanisms of the intestinal absorption of Mn in rats malnourished with a low protein‐low energy diet (M) for 4 weeks against controls fed a complete diet (C) during the same period. The absorption of Mn in the absence or in the presence of two small molecular weight ligands, citrate and L‐histidine, was studied by an in vivo procedure. In both M and C rats, jejunal Mn absorption decreased linearly with time and was enhanced by the presence of the low molecular weight ligands. The initial rate of absorption, for Mn alone, was higher in M than in C rats, but it was indistinguishable between both groups in the presence of either citrate or L‐histidine. Total Mn absorption, in midperfusion, was greater in M than in C animals with no ligands in the solutions (means ± SEM, M = 2,969 ± 923 vs. C = 654 ± 218 pmol/cm, p < 0.05). However, in the presence of citrate or L‐histidine, the well‐nourished rats absorbed more Mn than M rats. Also, water fluxes across the mucosa had a positive correlation with Mn transport when the ligands were present. This solvent drag of the trace element was not operant in the absence of citrate or L‐histidine. These data indicate that the jejunal mucosa of M rats absorbs Mn more effectively than C animals, independently from water fluxes and the presence of small molecular weight chelators. These substances do not alter the uptake of Mn in growth‐retarded rats, while they enhance the absorption of the trace metal in well‐fed animals.