Local and systemic effects of Na+/K+ATPase inhibition
1Institute of Clinical Pharmacology, F. Hoffmann La Roche, Basel, Switzerland.
European Journal of Clinical Investigation
|August 30, 2001
Summary
Cardiac glycosides enhance heart muscle contraction by inhibiting Na+/K+ ATPase, affecting ion flow and leading to both therapeutic and toxic effects. These actions influence cardiac function and systemic hemodynamics.
Area of Science:
- Pharmacology
- Cardiovascular Physiology
Background:
- Cardiac glycosides exert positive inotropic and electrophysiological effects on cardiac muscle.
- These effects are primarily mediated by the inhibition of the sodium-potassium adenosine triphosphatase (Na+/K+ ATPase) enzyme.
- The enzyme inhibition occurs via binding to a specific extracytoptoplasmic site on the alpha-subunit.
Purpose of the Study:
- To elucidate the mechanisms underlying the therapeutic and toxic effects of cardiac glycosides.
- To detail how Na+/K+ ATPase inhibition influences ionic flux and cardiac function.
- To explore the systemic and extracardiac consequences of cardiac glycoside action.
Main Methods:
- The study reviews the biochemical interactions of cardiac glycosides with Na+/K+ ATPase.
- It analyzes the resulting alterations in cellular ion concentrations (Na+, K+, Ca++).
- The research examines the impact of these ionic changes on cardiac action potentials, contractility, and hemodynamics.
Main Results:
- Na+/K+ ATPase inhibition leads to increased intracellular sodium and potassium loss, affecting action potential propagation.
- This inhibition potentiates cardiac glycoside effects in conditions like hypokalemia and hypomagnesaemia.
- Inhibition of Na+/Ca++ exchange enhances calcium mobilization, further promoting contractility.
Conclusions:
- Cardiac glycosides' local and systemic effects are directly linked to Na+/K+ ATPase inhibition and subsequent hemodynamic changes.
- Factors such as hypokalemia, hypomagnesaemia, and calcium homeostasis significantly modulate cardiac glycoside pharmacodynamics.
- Extracardiac effects, including vascular and CNS actions, may also stem from Na+/K+ ATPase inhibition at non-cardiac sites.
Related Concept Videos
01:48ATP Synthase: Mechanism
In animals, the mitochondrial F1F0 ATP synthase is the key protein that synthesizes ATP molecules through a complex catalytic mechanism. While the nuclear genome encodes the majority of ATP synthase subunits, the mitochondrial genome encodes some of the enzyme's most critical components. The formation of this multi-subunit enzyme is a complex multi-step process regulated at the level of transcription, translation, and assembly. Defects in one or more of these steps can result in decreased ATP...
01:23Local Anesthetics: Mechanism of Action
Local anesthetics (LAs) block sensory and motor impulses by inhibiting the sodium channels on the nerve cell membranes. This induces temporary loss of sensation, relieving pain in a specific body area.
Local anesthetics are amphiphilic molecules consisting of a hydrophobic aromatic part linked to a hydrophilic group by an ester or amide linkage. They are weak bases and are usually available as salts, which increases their solubility and stability. Once administered, LAs exist in the body either...
Local anesthetics are amphiphilic molecules consisting of a hydrophobic aromatic part linked to a hydrophilic group by an ester or amide linkage. They are weak bases and are usually available as salts, which increases their solubility and stability. Once administered, LAs exist in the body either...
01:13Local Anesthetics: Pharmacokinetics
The potency and duration of action of local anesthetics (LAs) are determined by their pharmacokinetics. Pharmacokinetics describes how LAs are absorbed, distributed, metabolized, and eliminated from the body. When administered to the vascular tissues, LAs are quickly absorbed and enter the systemic circulation, reducing their localized effects. Adding vasoconstrictors such as epinephrine to LAs reduces their absorption into the systemic circulation, making them clinically effective. The...
01:28Antihypertensive Drugs: Potassium-Sparing Diuretics
Liddle syndrome is a genetically inherited form of hypertension characterized by the overactivity of epithelial sodium channels in the nephron, the functional unit of the kidney. This heightened activity leads to increased sodium reabsorption and excessive excretion of potassium. To counteract this, potassium-sparing diuretics such as amiloride are used. They function by blocking these sodium channels, thereby reducing the influx of sodium into the epithelial cells and minimizing the loss of...
01:16Cellular Injury IV: Necrosis
Necrosis is a form of irreversible cell death caused by severe injury such as ischemia, toxins, or trauma. Unlike programmed cell death, it is an uncontrolled, pathological process that typically provokes inflammation in surrounding tissues.Pathophysiologic ChangesNecrosis begins when cells sustain critical damage, leading to swelling of organelles, particularly mitochondria, and rapid ATP depletion. As energy levels decline, membrane ion pumps fail, leading to calcium influx and eventually,...
01:21Cytotoxic Edema: Pathophysiology
Cytotoxic edema is a form of cerebral edema characterized by intracellular swelling of neurons, astrocytes, and other glial cells. It develops when the mechanisms responsible for maintaining ionic gradients across the cell membrane become impaired. Under normal physiological conditions, the sodium–potassium ATPase actively transports sodium ions out of the cell and potassium ions into the cell, preserving osmotic balance and enabling electrical signaling. This pump requires a continuous supply...