VASODILATIVE ACTIVITY IN BLACK FLY SALIVARY-GLANDS

Salivary gland extracts of several Simulium spp. were shown to contain vasodilative activity as measured by the rapid and persistent inducti on of erythema in response to intradermal injection into rabbit skin. Total salivary gland activities were approximately equal for S. vittat um, S. metallicum, S. bivittatum, and S. argus (titers of 0.03-0.02 pa irs of gland). Total gland activity in the highly anthropophilic speci es S. ochraceum, however, was an order of magnitude greater, with eryt hema produced by as little as 0.002 pairs of glands. Tests for physica l stability of the activities from two species (S. vittatum and S. och raceum) indicated that the vasodilators were proteinaceous and heat st able. A two-step, reversed-phase high-performance liquid chromatograph y (HPLC) procedure was developed that isolated both activities with si milar elution patterns. Homogeneity of the purified protein from S. vi ttatum was confirmed by capillary gel electrophoresis. Electrospray io nization mass spectroscopy of the S. vittatum protein detected a mass of 15,351 daltons. Similarity in elution times of the proteins from a TSK HPLC column predict some structural similarities between the S. vi ttatum and S. ochraceum vasodilator proteins.