Acute toxicity of βγ-CAT, a naturally existing non-lens βγ-crystallin and trefoil factor complex from frog Bombina maxima skin secretions

In vertebrates, non-lens βγ-crystallins are widely expressed in various tissues, but their functions are unknown. The molecular mechanisms of trefoil factors, initiators of mucosal healing and being greatly involved in tumorigenesis, have remained elusive. βγ-CAT is the first example of a naturally existing multifunctional protein complex of a non-lens βγ-crystallin and a trefoil factor from frog Bombina maxima skin secretions. Here we report the investigation of its in vivo toxic effects on mice and rabbits. The LD50 values of βγ-CAT on mice were determined to be 0.4 mg/kg and 20 μg/kg under intraperitoneal (i.p.) and intravenous (i.v.) injection, respectively. The mice subcutaneously injected with βγ-CAT (6 μg/g body weight) showed strong hyperaemia of subcutaneous capillary vessel, but no hemorrhagic spots were observed. Intravenous injection of βγ-CAT in rabbits (8–22 μg/kg body weight) caused a rapidly hypotensive effect and followed with cardiovascular collapse. Injection with βγ-CAT (22 μg/kg, i.v.) significantly decreased hematocrit (P < 0.05) and mean corpuscular volume (P < 0.05) of the rabbits in 5 min. At the same time, the counts of platelets and white blood cells were significantly decreased (P < 0.05), while the blood levels of glucose, lactate dehydrogenase and serum glutamic–oxaloacetic transaminase were significantly increased (P < 0.05). Furthermore, serials of tissues edema and damages were also observed. These results indicate that βγ-CAT rapidly caused several in vivo toxic effects on mammals and its lethal toxic potency was mainly contributed by hypotension and cardiovascular collapse, providing new clues for the understanding of the patho-physiological roles of non-lens βγ-crystallins and trefoil factors.