Chronic oral administration of rhamnogalacturonan-II dimer, a pectic polysaccharide, failed to accelerate body lead detoxification after chronic lead exposure in rats

Abstract

Lead is a ubiquitous heavy metal and its toxicity remains an important public health issue. In previous work, we reported that ingestion of rhamnogalacturonan-II dimer (dRGII), a pectic polysaccharide, may decrease intestinal absorption and status of Pb in rats. Here, we evaluated the potential detoxifying effect of different doses of dRGII after chronic oral Pb exposure in rats. For this purpose, six groups of ten male Wistar rats weighing 150 g were treated as follows: group A received a semi-purified control diet for 6 weeks; groups B, C, D, E and F received the same diet plus 3 mg Pb (as acetate) for 3 weeks. Group B was then killed. Groups C, D, E, and F continued to receive the semi-purified control diet containing 0, 2, 6 or 18 g dRGII/kg diet for 3 additional weeks. During the last 5 d, a Pb conventional balance study was performed. Rats were then anaesthetized and tissues were sampled for Pb and essential minerals assay. The results showed that residual Pb in the added dRGII was not available for absorption. However, the added dRGII failed to induce any significant increase in faecal or urinary Pb excretion. Consequently, at the end of the study the intestinal Pb absorption and balance remained unchanged in the animals receiving the different doses of dRGII. In line with this, we showed that dRGII administration was not effective in decreasing tibia or kidney Pb levels in rats. In conclusion, Pb complexed by dRGII in fruits and vegetables and fruit juice is thus mostly unavailable for intestinal absorption. However, the addition of dRGII after chronic Pb exposure does not help Pb detoxification.