Circulating vasotocin in the snake Bothrops jararaca.

Area of Science:

• Comparative Endocrinology
• Snake Physiology
• Neuroendocrinology

Background:

• Vasotocin (VT) is a key neurohypophyseal hormone in non-mammalian vertebrates, analogous to vasopressin and oxytocin in mammals.
• Understanding VT presence and function in reptiles, like the snake Bothrops jararaca (Bj), is crucial for comparative physiology.
• Previous studies have suggested VT's role, but direct evidence in Bj blood and plasma remained limited.

Purpose of the Study:

• To biochemically and pharmacologically investigate the presence and characteristics of vasotocin in the blood and plasma of Bothrops jararaca.
• To determine the physiological activities associated with Bj blood and plasma extracts.
• To elucidate the forms (free vs. bound) and equilibrium of circulating vasotocin in Bj.

Main Methods:

• Extraction of XE-64 from Bj blood and plasma.
• Pharmacological assays in rats (antidiuretic, hypotensive) and isolated rat uterus (contractile, oxytocic).
• Dialysis, thioglycollate inhibition, EDTA and Sep-Pak C18 extraction, and High-Performance Liquid Chromatography (HPLC) for VT characterization.

Main Results:

• Bj blood extracts exhibited significant antidiuretic, hypotensive, and uterine contractile activities, with the latter being dialyzable and thioglycollate-sensitive.
• Bj plasma extracts showed partial antidiuretic activity and notable oxytocic properties.
• Enhanced recovery and characterization of vasotocin were achieved using EDTA and Sep-Pak C18 extraction followed by HPLC.

Conclusions:

• The results confirm the presence of vasotocin in the circulating blood and plasma of Bothrops jararaca.
• Both free and bound forms of vasotocin are present, existing in an equilibrium influenced by enzymatic hydrolysis.
• The identified pharmacological activities support vasotocin's physiological roles in snakes, including fluid balance and reproductive functions.