Human atrial natriuretic polypeptides (hANP): purification, structure synthesis and biological activity

Area of Science:

• Biochemistry
• Endocrinology
• Physiology

Background:

• Human atrial extract contains natriuretic factors.
• These factors play a role in regulating blood pressure and fluid balance.

Purpose of the Study:

• To purify and sequence natriuretic polypeptides from human atrial extract.
• To characterize the molecular forms and biological activities of these polypeptides.

Main Methods:

• In vitro assay using chick rectum for relaxant activity.
• Purification and sequencing of polypeptides.
• In vivo studies in rats to assess physiological effects.

Main Results:

• Three distinct human atrial natriuretic polypeptides (hANP) were identified: alpha- (3 kDa), beta- (6 kDa), and gamma- (13 kDa).
• Gamma-hANP (126 residues) contains the alpha-hANP sequence (28 amino acids) at its C-terminus.
• Beta-hANP is an antiparallel dimer of alpha-hANP.
• Synthetic alpha-hANP induced diuresis, natriuresis, and hypotension in rats.
• Beta- and gamma-hANP showed significantly lower natriuretic activity compared to alpha-hANP on a molar basis.

Conclusions:

• Alpha-, beta-, and gamma-hANP are distinct natriuretic factors present in human atria.
• Alpha-hANP is the most potent form in terms of diuretic, natriuretic, and hypotensive activity.
• The different molecular forms of hANP may have varying physiological roles.