The effect of chronic administration of trisodium nitrilotriacetate (Na3NTA) on the haversian remodelling system in dogs.

Trisodium nitrilotriacetate from the environment is reported to accumulate in bone. Two skeletally mature male littermate beagles were administered Na3NTA in a concentration of 2.5 mg/kg body weight in their drinking water for a period of 7 months. Rib biopsies were obtained from the dogs after fluorescent labelling before and at the end of the experimental period. Blood levels of zinc were measured at the same times. Twenty-two similar dogs from the same colony acted as controls. We noticed a decrease in radial closure rates and percent osteoid seams labelled between the experimental and the control animals which was statistically significant at the 0.05 level. The serum levels of iPTH and the bone levels of zinc showed no statistically significant difference. Accepting the fact that the treatment population was small and that the changes observed--although statistically significant--were minimal, it cannot be discounted that the exposure of these animals to Na3NTA for a longer period of time would not have had a more adverse effect on haversian bone remodelling activity.