CONTRACTILITY AND INHIBITION OF PROTEIN PHOSPHATASES BY CANTHARIDIN

1. Cantharidin is a natural defensive toxicant: produced by blister be etles. 2. Cantharidin shares structural similarity with highly toxic c ommercial herbicides (e.g., endothall, endothall anhydride and endotha ll thioanhydride), 3. Cantharidin inhibits the activity of purified ca talytic subunits of serine/threonine protein phosphatases (PP) type 1 and type 2A. 4. Cantharidin increases force of contraction in isolated myocardial and vascular preparations. 5. Cantharidin enhances the pho sphorylation state of myocardial and vascular regulatory proteins. 6. Cantharidin is a valuable tool for studying the function of PP in regu latory phosphorylation-dephosphorylation events. (C) 1998 Elsevier Sci ence Inc.