Characteristics of antischistosomal benzodiazepine binding sites in Schistosoma mansoni

The benzodiazepines, clonazepam and Ro 11-3128, have been identified as antischistosomal drugs (Stohler, 1978). Using [14C] Ro 11-3128 or [3H] clonazepam, we were able to demonstrate that male S. mansoni can specifically bind these labeled drugs. The binding sites on this parasite displayed characteristics of saturability and low affinity. The affinity of various benzodiazepines for the binding site on intact schistosomes correlated with their antischistosomal efficacy. Binding was markedly altered by agents known to destroy membrane integrity. Combined with previous studies (Pax et al., 1978), this work suggests that a specific, benzodiazepine binding site may be located on the epidermis of male S. mansoni.