B-type natriuretic peptide isolated from frog cardiac ventricles

Area of Science:

• Cardiovascular Physiology
• Comparative Endocrinology
• Biochemistry

Background:

• Natriuretic peptides play crucial roles in cardiovascular homeostasis.
• B-type natriuretic peptide (BNP) is a key regulator of blood pressure and fluid balance.
• Understanding natriuretic peptide evolution across species provides insights into physiological adaptations.

Purpose of the Study:

• To isolate and characterize a novel natriuretic peptide from the bullfrog (Rana catesbeiana) cardiac ventricles.
• To determine the sequence, structural features, and physiological activities of this newly identified peptide.
• To compare bullfrog BNP with other known natriuretic peptides, particularly in terms of sequence homology and biological potency.

Main Methods:

• Isolation and purification of the peptide from bullfrog cardiac ventricles.
• Amino acid sequencing to determine the peptide's structure.
• In vivo studies in bullfrogs to assess vasodepressor activity.
• In vivo studies in rats to evaluate vasodepressor, natriuretic, and diuretic potencies.

Main Results:

• A novel 27-amino acid natriuretic peptide, named bullfrog BNP, was isolated.
• Bullfrog BNP shares 74% sequence identity with chicken BNP, suggesting a tetrapod-type BNP.
• The peptide exhibited potent dose-dependent arterial blood pressure reduction in bullfrogs, exceeding human ANP's potency.
• In rats, bullfrog BNP displayed vasodepressor, natriuretic, and diuretic activities, though with lower potency than human ANP.

Conclusions:

• Semi-aquatic amphibians like the bullfrog possess a tetrapod-type BNP in their ventricles.
• Bullfrog BNP is structurally distinct, with an elongated, non-amidated C-terminus.
• This peptide represents a potent endogenous regulator of blood pressure in amphibians and retains cross-species activity.