In vitro human lymphocyte PHA response- the heterogeneous effect of methylazoxymethanol acetate.

Abstract

In earlier studies on the effect of methylazoxymethanol acetate (MAM AC), a mutagen, teratogen and carcinogen, upon sister chromatid exchange, the concentrations tested in short-term lymphocyte cultures from 9 individuals were not identical for each person. (The concentrations were derived from dose-effect curves for each individual, involving the quantity of MAM AC [5...50...80 µg/ml] versus blast transformation using PHA.) The differences obtained between the curves were investigated further by repeating the dose-effect curves in cell cultures derived from 10 normal male individuals, except that Ficoll-Hypaque-purified mononuclear cells were cultured at a concentration of 3 × 10<sup>5</sup> viable cells/ml. Five identical microwell cultures (150 µl) were tested for each variable within an individual experiment. Controls with and without PHA (PHA+, PHA-) were included. The results show that not all individuals’ cultures exhibited the same PHA response for each concentration of MAM AC. In the 10 cases studied: (1) dose-effect curves were not uniform for all experiments; (2) the percentages of <sup>3</sup>H-incorporation at 5 µg/ml of MAM AC compared to that of PHA+ controls were not the same across experiments; depending on the experiment, 5 µg/ml significantly increased, reduced or had no effect on PHA when <sup>3</sup>H-uptake was compared to PHA+ control levels; (3) when mean log values of the above percentages were plotted with their confidence intervals, striking differences were exhibited between individuals or groups of individuals; (4) the TD<sub>50</sub> values, referred to as the concentration of MAM AC at which half as much label was incorporated as compared to PHA+ control cultures, were different, and (5) the lowest MAM AC concentrations effective in reducing <sup>3</sup>H-uptake levels to those of PHA-controls were not the same. Familial and/or laboratory animal studies will demonstrate whether these differences are genetically determined.