Reference toxins for antivenin standardization.

Potency determinations in mice of venom samples from snakes of the species Bothrops jararaca, which had been caught in an area of less than 10 000 km(2), gave the following principal results:(1) Various methods of drying-i.e., closed and continuous vacuum-drying at 5 degrees and 37 degrees C and freeze-drying (lyophilization)-had no different effect on the potency of venoms.(2) Venom samples which display no differences in the final results of intravenous assay may be distinguishable if the observation time is limited to one or two hours.(3) Venom samples obtained from snakes caught no more than about 50 km apart may be of different potencies.(4) Different titres may be obtained for an antivenin, if different samples of venom from the same snake species are employed as reference preparations in the assay.From physiological experiments on dogs and rabbits, in conjunction with observations made in tests on mice, it is evident that B. jararaca venom causes death in circulatory collapse through a mechanism which is as yet unknown. Two physiologically (and probably immunologically) distinct hypotensory factors seem to be present in this venom.The conclusions drawn from the investigation is that consistent and reproducible reference preparations of snake venoms for antivenin assay can probably be obtained only from snakes that are bred and kept in captivity under constant environmental conditions.