Circulating vasotocin in the snake Bothrops jararaca.

1. There is biochemical and pharmacological evidence to suggest the presence of vasotocin in the blood and plasma of the snake Bothrops jararaca (Bj). 2. XE-64 extracts from Bj blood showed antidiuretic and hypotensive activities in rats and a contractile effect on rat isolated uterus, which was totally dialysable and inhibited by thioglycollate. 3. Extracts from Bj whole plasma presented an antidiuretic activity which was only partially dialysable. 4. The plasma extracts also showed oxytocic properties. 5. When EDTA and Sep-Pak C18 extraction were used, a better recovery and characterization of vasotocin by HPLC was obtained. 6. These results indicate the occurrence of free and bound circulating vasotocin in Bj, in an equilibrium dependent of its enzymatic hydrolysis.