Ontogenetic differences in cardiac sensitivity to verapamil in rats

Area of Science:

• Cardiovascular Pharmacology
• Developmental Physiology

Background:

• Verapamil is a calcium channel blocker used to treat various cardiovascular conditions.
• Understanding the impact of verapamil on developing hearts is crucial for safe therapeutic use.

Purpose of the Study:

• To investigate the age-dependent negative inotropic effects of verapamil on the isolated rat right ventricle.
• To assess the relationship between verapamil administration and mortality rates in developing rats.

Main Methods:

• Isolated right ventricles from male Wistar rats (3, 15, 30, and 90 days old) were studied.
• Verapamil's effect on the amplitude of isotonic contractions (AIC) was measured after incubation in oxygenated, glucose-free solution.
• Mortality rates in verapamil-treated rats were recorded.

Main Results:

• A significant age-dependent negative inotropic response to verapamil was observed.
• The reduction in AIC was most pronounced in 3-day-old rats (2.6%) compared to older groups (e.g., 90-day-old rats: 74.1%).
• Mortality rates increased as the age of the rats decreased, indicating higher toxicity in younger animals.

Conclusions:

• Rat myocardial sensitivity to verapamil increases with decreasing age.
• The negative inotropic effect of verapamil is significantly more potent in very young animals.
• Therapeutic use of verapamil in newborns and infants may pose a considerable risk due to heightened sensitivity.