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j. Soc. Cosmet. Chem., 44, 153-162 (May/June 1993) The pollen tube growth test: A new alternative to the Draize eye irritation assay UDO KRISTEN, UDO HOPPE, and WOLFGANG PAPE, Institut fiir Allgemeine Botani K, Universitiit, Ohnhorststrasse 18, D-2000 Hamburg 52, and PGU Research Center, Beiersdorf AG, Unnastrasse 48, 2000 Hamburg 20, Germany. Received January 24, 1992. Synopsis The pollen tube growth test (PTG test), recently developed to detect the cytotoxicity of bioactive chemicals, is compared with the well-established Draize eye irritation assay. The PTG test, based on the growth response of in vitro growing tobacco pollen tubes, is described in detail. Comparison of the corresponding growth response data of both assays, using 22 tensides as test substances, reveals highly significant rank correlations (r = 0.73, p = 0.0018). In both assays, the most toxic substances are among the group of anionic sulfate/sulfonate tensides, whereas the nonionic tensides show moderate effects. The results of the comparison clearly demonstrate that the PTG test is well suited to screen irritation potentials of surfactants and provides reliable results with good reproducibility. Moreover, the PTG test is inexpensive and helps to reduce or even avoid painful animal testing in this application. INTRODUCTION For ethical and economic reasons and because of new animal protection laws, powerful methods must be developed to replace animal experiments. Tissue and cell cultures of animal, human, and plant origin have given good results as alternative systems for toxicological testing of certain classes of substances. However, no alternative method is able to cover the whole range of lethal, sublethal, and chronic toxicity in vertebrates (including man) of all potentially toxic chemical compounds. Of the almost ten million registered substances that could be a toxicological threat to the whole biosphere [ex- trapolated according to Koch (1)], about 0.5% pose a real ecological problem. The potential threat of these 50,000 substances to the environment should be determined by means of suitable toxicological methods while keeping animal experiments to a mini- mum. It is only with a broad range of different alternatives to animal experiments that this can be accomplished. Of the plant organs, tissues and cell types used so far that are suitable for toxicological test methods, the microspores (pollen grains) and their germination product, the pollen tube, have given especially good results. Although germinating pollen grains and 153