This study looked at how toxic
proteins in
venoms of adult Australian eastern Brown snakes Pseudonaja textilis from South Australian and Queensland populations interact with physiological functions of the lab SD rat Rattus norvegicus.
Circulatory collapse and incoagulable blood occurred instantly after injection of
venom under the dorsal skin of anaesthetised and mechanically ventilated rats in an imitation of a P. textilis
bite.
Intravenous injection of purified P. textilis (Mackay, QLD)
venom prothrombin activator
proteins caused instant failure of circulation, testifying of high toxicity of these
proteins and suggesting their role in rapid incapacitation of rodent prey. The hypothesis is further supported by
circulatory collapse occurring instantly despite
artificial respiration in envenomed rats and the finding of extremely high
venom procoagulant potency in rat plasma. LC-MS and physiology assays revealed divergent
venom composition and
biological activity of South Australian (Barossa locality) and Queensland (Mackay locality) populations, which may be driven by selection for different prey. The Queensland
venom of P. textilis was found to be more procoagulant and to exhibit predominately presynaptic neurotoxicity, while the South Australian
venom contained diverse postsynaptic type II and III α-
neurotoxins in addition to the presynaptic
neurotoxins and caused significantly faster onset of neuromuscular blockade in the rat phrenic nerve-diaphragm preparation. LC-MS analysis found evidence of multiple
coagulation factor X-like
proteins in P. textilis
venoms, including a match to P. textilis
coagulation factor X isoform 2, previously known to be expressed only in the liver.