Chromosome Breakage by Pyrrolizidine Alkaloids and Modification of the Effect by Cysteine

SUMMARYThe author has studied the cytological effect, in onion root tips, of 6 pyrrolizidine alkaloids already known to be hepatotoxic in mammals and mutagenic in Drosophila.A comparative analysis of the effect of treatments with solutions of identical concentrations (3.2, 1.6 and 0.8 × 10—3M/1) and for identical durations (24-hour treatment followed by one, two and several days of recovery into water) has shown that: 1. - all the alkaloids studied are able to induce chromosomal damage, the most active being lasiocarpine, heliotrine and jacobine;2. - no qualitative difference in action exists between the 6 alkaloids: the aberrations observed are almost exclusively of chromatid type, even in recovery experiments of long duration, in which aberrations due to chromosome breakage in the pre-split phase should occur;3. - a characteristics common to the alkaloids studied is the high relative frequency of chromatid bridges to fragments. Such a high reunion ability of broken ends has not been observed so far in Allium, neither with radiations nor with chemical mutagens.Investigations on possible protective effects have shown that cysteine, when used in simultaneous treatments with lasiocarpine and monocrotaline, can riduce as much as 85% the chromosomal damage induced by the two alkaloids.The data obtained seem to offer indications of a lack of correlation between toxic effect and chromosome breaking effect in pyrrolizidine alkaloids.