Mitochondrial toxicity detected in a health product with a boar spermatozoan bioassay

By Hoornstra, D. - Andersson, M.A. - Johansson, T. - Pirhonen, T. - Hatakka, M. - Salkinoja-Salonen, M.S.

Seaweed and organic alfalfa capsules sold as "health promoting" products had repeatedly caused emesis in a consumer. Using the boar spermatozoan bioassay, the capsule contents were found to contain a toxic substance that inhibited boar sperm motility and depolarised mitochondria at low exposure concentrations of 10 microgram/ml. The capsule also contained high amounts (10(5)-10(7) cfu/g), of endospore-forming bacteria and Streptomyces-like bacteria. Bacteria from the capsule produced toxic substances when cultured in the laboratory. Three different toxic responses were provoked in the spermatozoa exposed to extracts from the Streptomyces-like isolates: a) hyperpolarisation of the plasma membrane and depolarisation of the mitochondria; b) depolarisation of mitochondria similar to that caused by the capsule content extract; and c) motility inhibition, with no observed change of any cytosolic transmembrane potential. Membrane potential changes in the sperm cells exposed to the bacterial extracts were similar to those provoked by exposure to valinomycin and bafilomycin A1, to nigericin, and to oligomycin and ionomycin, respectively. Extracts prepared from Bacillus isolated from the capsule non-specifically depolarised all the cellular transmembrane potentials. The results demonstrate the potential value of a cell toxicity assay with boar spermatozoa for detecting hazardous substances in products intended for human consumption, without whole-animal exposure or using fetal calf serum for cell cultures.