ABSTRACT
Aromatic hydrocarbons of low molecular weight, hydroxy and N-methylcarbamate derivatives were tested for mutagenicity by the reversion of histidine-dependent Salmonella typhimurium TA98 and TA1535 in the presence of a rat-liver 9000 X g supernatant fraction. The presence of 2 or 3 aromatic rings resulted in a weak increase in revertants. Hydroxylation and carbamylation of aromatic rings increased the mutagenic activity of these aromatic compounds. In order to evaluate the structure-activity relationship, the specific molecular connectivity indices were calculated. A significant inverse relationship exists between mutagenicity and zero- and second-order specific molecular connectivity indices. Only compounds with second-order specific molecular connectivity indices lower than 0.300 increased mutagenic activity.
Subject(s)
Carbamates/toxicity , Mutation/drug effects , Salmonella typhimurium/drug effects , Benzyl Compounds/toxicity , Biotransformation , Biphenyl Compounds/toxicity , Microsomes, Liver/metabolism , Naphthalenes/toxicity , Phenanthrenes/toxicity , Structure-Activity RelationshipABSTRACT
Thirty-one carbanilate derivatives were assayed for their capabilities to inhibit the ATPase activity of a plasma membrane fraction from Acer pseudoplatanus cells. At a concentration of 100 micromolar, nine compounds strongly inhibited the ATPase activity, with I(50) ranging from 14.5 micromolar to 35 micromolar. These molecules were also inhibitory to plasma membrane ATPases of other origins: plant (maize shoot), yeast (Schizosaccharomyces pombe), and animal (dog kidney). The most efficient molecule appeared to be 2,2,2-trichloroethyl 3,4-dichlorocarbanilate.
ABSTRACT
2,2,2-Trichloroethyl 3,4-dichlorocarbanilate (SW26) is toxic for Acer pseudoplatanus cell cultures. It inhibited the cellular proton extrusion and depolarized the plasmalemma. In vitro, it inhibited the plasma membrane ATPase. SW 26 was also inhibitory to membrane ATPases of other origins-plant (maize shoot), fungus (Schizosaccharomyces pombe), and animal (dog kidney)-with about the same efficiency (7.5 micromolar < I(50) < 22 micromolar). It did not inhibit the oligomycin-sensitive ATPase from purified plant mitochondria, nor molybdate-sensitive soluble phosphatases. SW26 was more specific for plasma membrane ATPases than diethylstilbestrol or vanadate. A Lineweaver-Burk plot analysis showed that inhibition kinetics were purely noncompetitive (K(i) = 14.7 micromolar) below 20 micromolar. Above this concentration, the inhibition pattern was not consistent with Michaelis-Menten kinetics, and a Hill plot representation revealed a positive cooperativity.
