INTERACTIONS AND DISTRIBUTION OF MERCURY COMPOUNDS IN THE INTESTINE OF FISH‐IMPLICATIONS FOR AQUACULTURE

Aquaculture facilities are often located in the proximity of agricultural, industrial, or urban sources of pollution. Utilization of water downstream from pollution sources is a general concern to aquaculturists. Rivers and coastal waters receive heavy metals from industrial and urban wastes and effluents. In most aquatic animals, the main route of heavy metal entry is via food and drink. In addition to the accumulation of heavy metals in aquatic species, we and others have shown that HgCl₂ and CH₃HgCl inhibit intestinal absorption of amino acids and sugars. Here we present data to show the generality of this effect among several species. The data also show that HgCl₂ is a more potent inhibitor than CH₃HgCl. In order to further elucidate the mechanisms of action of mercury, we have examined the movement of ²⁰³HgCl₂ and CH₃²⁰³HgCl from the intestinal lumen to the blood using a free swinnning in vivo procedure in the toadfish, Opsanus tau. Intestinal tissue and luminal fluid were analyzed after each incubation period. It was observed that both compounds appear in the tissue fraction within the first hour. CH₃HgCl rapidly transfers to the blood, while HgCl₂ exhibits a slow but evident transfer. Much of the HgCl₂ in the tissue fraction was carried back to the luminal fluid by the mucus, suggesting binding to the luminal surface with little intracellular entry. CH₃HgCl mainly moved into the tissue and then the blood with little or none being returned to the luminal fluid bound to mucus. Differences in the site of action of these two compounds was suggested.