Histochemical Observations on the Permeation of Heavy Metals into Taste Buds of Goldfish

Abstract

The present study was aimed at confirming whether metal-permeation into taste cells was responsible for the histological damage of taste buds of goldfish exposed to heavy metals. Histochemical observations employing TIMM's sulphide-silver method were made on the taste buds located in the palatal organs of goldfish exposed to 10^-4M solutions of mercuric chloride, copper sulphate and zinc chloride, and 10^-3M solutions of copper sulphate, zinc chloride and lead nitrate, Results revealed that the rate of metal-permeation into taste cells varied with the kind of metal, the concentration of the metallic ions in the medium, and the duration of exposure. In terms of permeation rate the sequence of metals was found to be mercury, copper, zinc and lead. Mercury damaged not only the taste buds but the entire epithelial layers within 30min. Lead affected mucous cells more than the taste buds. The results suggest that histological damage is associated with a ?? preceded by metal-permeation. During the early phase of exposure, mercury, copp ?? (10^-4M) and zinc (10^-3M) were found to permeate into one type of taste bud cell at ?? faster rate than into others.