EFFECTS OF BENZOFURAN AND 7 BENZOFURAN DERIVATIVES INCLUDING 4 CARBAMATE INSECTICIDES IN THE IN-VITRO PORCINE BRAIN TUBULIN ASSEMBLY ASSAY AND DESCRIPTION OF A NEW APPROACH FOR THE EVALUATION OF THE TEST DATA

The influence of benzofuran and 7 benzofuran derivatives, including th e carbamate insecticides benfuracarb, carbofuran, carbosulfan, and fur athiocarb, on the in vitro assembly kinetics of porcine brain tubulin was investigated. A new approach to the evaluation of the raw data was made based on polynomial regression and the calculation of a polynomi al function of the 11th degree fitting the raw data. By this procedure it is possible to calculate the parameters defining the shape of the absorbance curves and more parameters than those used so far can be in cluded in the analysis of substance effects. In detail, the following curve parameters of the dependence of optical absorption on time were included in the evaluation of the substances of interest: the differen ce between maximum and minimum absorbance as a measure for the polymer ization degree, the coordinates of the turning point of the curve, the slope of the tangent at the turning point which represents the maximu m reaction velocity, the mean slope between the points with 10% absorb ance increase and 90% absorbance increase and the duration of the lag phase. Out of the eight compounds tested, only the carbamate insectici des had distinct effects on the in vitro polymerization of tubulin, wh ereas benzofuran and the three 2,3-dihydro-2,2-dimethylbenzofuran deri vatives without a carbamate function were inactive. Benfuracarb, carbo furan, carbosulfan, and furathiocarb led to a dose-dependent reduction of the polymerization degree of tubulin as well as to reduction of th e maximum and mean reaction velocities. The strongest effects were obt ained with furathiocarb and benfuracarb.