Protein phosphatase-inhibiting activity in cyanobacteria from alpine lakes in Switzerland

Abstract

Abstract To elucidate the cause of unexplainable deaths of calves and heifers on alpine pastures in eastern Switzerland, water bodies were examined for cyanobacteria (blue-green algae) and their protein phosphatase-inhibiting activity, i.e. their potential hepatotoxicity. The algal populations in the waters examined consisted mostly of benthic cyanobacteria, forming large, dense mats on the surface of sediments and on submerged rocks. The mats were also frequently found floating on the surface of the water. Many samples of algal mats whose extracts showed protein phosphatase inhibition were dominated by Oscillatoria limosa C. Agardh ex Gomont. Out of a total of 99 samples from six sites, 27 showed significant protein phosphatase-inhibiting activity. Protein phosphatase inhibition corresponded to 1–1250 nmol microcystin-LR equivalents/g water-soluble proteins. The strength of inhibition differed from site to site and during the course of summer and autumn, being very low in July and October and highest in ...