The enhancement by caffeine of the frequencies of chromosomal aberrations induced in plant and animal cells by chemical and physical agents

Abstract

Summary Caffeine potentiation of induced chromosome damage was studied. The results are presented and discussed under four major headings: the dependence of the potentiation on (1) the type of chromosome-breaking agent, (2) the type of material, (3) the molecular structure of the potentiating agent, and (4) environmental and metabolic factors. The frequencies of chromosomal aberrations produced in plant and animal cells by maleic hydrazide (MH), 4-nitroquinoline- I -oxide (4NQO), ultraviolet irradiation and a number of mono- and poly-functional alkylating agents was dramatically increased by post-treatments with caffeine. Results with maleic hydrazide indicate that, for this type of agent, potentiation is obtained only when the cells are exposed to caffeine during the S-phase. The chromosome damage produced by X-rays in bean roots was increased by post-treatments with caffeine when cells were irradiated in G 2 or prophase, but not in G 1 or S. Bleomycin (BLM)-induced chromosome damage was increased by caffeine both in G 2 -prophase cells and in S cells. Caffeine potentiation of thiotepa-induced chromosome damage was obtained in root tips of Vicia faba and Allium proliferum as well as in cell cultures of the Chinese hamster. No potentiation was obtained in the human cell line LU106. Post-treatments with methylated oxypurines did not produce any marked change in the proportions of the various types of aberration, but merely increased the frequencies of the aberrations characteristic of the thiotepa effect in plant and animal cells. The relative activities of the methylated oxypurines differed depending on the material. Eight methylated oxypurines were tested for their ability to potentiate the chromosome damage produced by thiotepa in Chinese hamster cells and in bean ( Vicia faba ) roots. In the latter material caffeine produced the strongest potentiation, whereas in Chinese hamster cells, caffeine was surpassed by 8-chlorocaffeine (CC) with regard to potentiating activity. Tetramethyluric acid (TMU) was almost inactive in both materials. In bean roots a 5-h post-treatment with 2.5 ·10 −3 M caffeine produced an almost 8-fold increase of the thiotepa-induced aberration frequency when given at 25° and 5 h after thiotepa. A similar caffeine post-treatment given at 10° was practically without effect. In contrast, caffeine potentiation of the chromosome damage produced by MH, azaserine and methyl methanesulphonate (MMS) was almost as strong when roots were exposed to caffeine at 10° as when they were exposed at 25°.