Venom of the Australian rough-scaled snake, Tropidechis carinatus: Lethal potency and electrophysiological actions

Abstract

A series of experiments to define the lethal potency ( ld 50) and electrophysiological properties of the venom of the Australian Rough-scaled Snake ( Tropidechis carinatus) are described. Crude pooled venom contains at least five fractions which were separated using liquid chromatography and high pressure liquid chromatography techniques (Fractions I–V). ld 50 studies are reported using each of these fractions, with data for both adult and neonatal mice. Fraction I (mol. wt > 100,000) was essentially non-toxic. Fraction IV (mol. wt ≤ 10,000) and Fraction V (mol. wt < 1,000) were potent toxic components with ld 50's (s.c. injection; fraction in 0.1% bovine serum albumin and 0.85% saline; neonatal mice) of 0.04 mg/kg and 0.06 mg/kg respectively. ld 50's for the whole crude venom were similar in both adult and neonatal mice. Electrophysiological studies using a Bulbring preparation (rat isolated phrenic nerve - hemidiaphragm) indicated that Fractions I, IIa and IIb were inactive. Fraction IV (mol. wt ≤ 10,000) caused rapid neuromuscular blockade which appeared to be irreversible. Neurophysiological experiments with a rat isolated extensor digitorum longus muscle preparation suggested that the major toxic activity of the whole venom resides in Fractions III and IV, and that both of these fractions have presynaptic and postsynaptic action.