Ouabain-induced mechanical toxicity: aberrations in left ventricular function, calcium concentration, and...

Area of Science:

• Cardiology
• Cell Biology
• Pharmacology

Background:

• Digitalis glycosides are commonly used to treat heart failure.
• Myocardial mechanical dysfunction can occur with digitalis treatment.
• The cellular mechanisms underlying digitalis-induced cardiotoxicity require further elucidation.

Purpose of the Study:

• To investigate whether digitalis-induced myocardial mechanical dysfunction is associated with ultrastructural damage.
• To determine if excessive calcium accumulation in cardiac cells accompanies digitalis toxicity.
• To explore the relationship between cellular calcium levels and mechanical dysfunction in the digitalis-treated heart.

Main Methods:

• Isolated rabbit heart model used for experimentation.
• Ouabain administered at concentrations of 1.2 or 2.4 microM.
• Assessment of systolic and end-diastolic pressure, ultrastructural changes, and cellular calcium concentration.

Main Results:

• Ouabain induced transient systolic pressure increase followed by a continuous decrease.
• Progressive increase in end-diastolic pressure observed with diminishing systolic pressure.
• Ultrastructural abnormalities included swollen mitochondria, hypercontracted sarcomeres, and myofibrillar disruption.
• Left ventricular cellular calcium concentration significantly increased and correlated with end-diastolic pressure.
• Reduced perfusate calcium did not affect ouabain-stimulated calcium uptake.

Conclusions:

• Digitalis-induced mechanical toxicity in the heart is linked to excessive cellular calcium uptake.
• Ultrastructural aberrations in digitalis-treated hearts are associated with increased intracellular calcium.
• Excessive calcium accumulation contributes to impaired mechanical performance and cellular damage in digitalis cardiotoxicity.