Vasopressin antagonism in the squirrel monkey (Saimiri sciureus).

Area of Science:

• Nephrology
• Pharmacology
• Endocrinology

Background:

• Vasopressin plays a crucial role in regulating water balance.
• Developing selective vasopressin antagonists is key for managing fluid balance disorders.

Purpose of the Study:

• To investigate the efficacy of vasopressin antagonists in inducing aquaresis in a primate model.
• To correlate in vitro antagonist activity with in vivo aquaretic effects.

Main Methods:

• Administration of vasopressin antagonists (i.p. or i.v.) to squirrel monkeys (Saimiri sciureus).
• In vitro evaluation of antagonism against vasopressin-stimulated renal medullary adenylate cyclase.
• In vivo assessment of aquaresis and electrolyte excretion.

Main Results:

• Vasopressin antagonists induced significant water diuresis (aquaresis) in squirrel monkeys.
• Antagonists with D-tyrosine (alkyl) substitutions at position 2 showed the highest potency both in vitro and in vivo.
• A strong positive correlation (r = 0.7880, P < .05) was observed between in vitro and in vivo potencies.
• Antagonists effectively blocked the antidiuretic effect of exogenous vasopressin.
• Aquaresis onset was rapid (within 30 min) following i.v. administration, with a duration exceeding 120 min.

Conclusions:

• Vasopressin antagonism effectively leads to aquaresis in primates.
• D-tyrosine substituted vasopressin antagonists are potent aquaretic agents.
• These findings support the therapeutic potential of vasopressin antagonists for conditions involving water retention.