Fish-scale photometry and in vitro cytotoxicity

Abstract

Certain fish scales contain thousands of black pigment cells (melanophores). Electrical stimulation of such a scale causes intrinsic nerves to release noradrenaline, which in turn aggregates the pigment within each melanophore. The aggregation is readily quantified by the aid of a simple fish-scale photometer. The probability of detecting toxic effects of chemicals (and their mode of action) is supposed to be quite good in such a system. The present contribution describes fish-scale photometry for in vitro estimation of acute toxicity of the first ten MEIC (Multicentre Evaluation of in vitro Cytotoxity) chemicals. The IC 50 (50% inhibition of nerve-induced pigment aggregation) values of the tested chemicals (except one) are close to or far below the known lethal blood concentrations in man. By comparing these IC 50 values with those of exogenously added noradrenaline, it is concluded that most of the tested chemicals mainly inhibit the nerve function. The present results suggest that fish-scale photometry may be of potential value as an inexpensive toxicity screening method.