Plasma endogenous sodium pump inhibitor in essential hypertension

Area of Science:

• Cardiovascular Physiology
• Endocrinology
• Biochemistry

Background:

• Hypertension is a complex cardiovascular disease with multifactorial origins.
• Circulating factors influencing the sodium-potassium pump (Na+, K+-ATPase) are implicated in blood pressure regulation.
• Endogenous digitalis-like substances have been hypothesized as potential contributors to hypertension.

Purpose of the Study:

• To investigate the presence and characteristics of circulating Na+, K+-ATPase inhibitors in essential hypertensive subjects.
• To determine if these inhibitors share properties with known cardiac glycosides like ouabain.
• To explore the potential link between these endogenous inhibitors and the pathophysiology of hypertension.

Main Methods:

• Assay of ouabain binding to the Na+, K+-ATPase in plasma extracts.
• Measurement of Na+, K+-ATPase activity inhibition by plasma fractions.
• Analysis of Na+-dependent serotonin uptake inhibition in platelets.
• Intracerebroventricular injection of plasma fractions in animal models to assess blood pressure effects.

Main Results:

• Plasma extracts from essential hypertensive subjects and normotensive offspring of hypertensive parents showed potent inhibition of ouabain binding and Na+, K+-ATPase activity.
• Three distinct plasma fractions exhibited ouabain-like properties, including competition for binding and inhibition of enzyme and transporter activity.
• One fraction, when administered intracerebroventricularly, induced a significant rise in blood pressure, similar to ouabain.

Conclusions:

• These findings demonstrate the presence of endogenous digitalis-like substances in the plasma of individuals with hypertension.
• These substances likely interfere with the Na+, K+-ATPase, potentially contributing to elevated blood pressure.
• Further research is warranted to identify these compounds and elucidate their precise role in the development and maintenance of hypertension.