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Effects of mibefradil on uterine contractility
Keerai T Asokan1, Souvendra N Sarkar, Santosh K Mishra
1Division of Pharmacology and Toxicology, Indian Veterinary Research Institute, Izatnagar, 243 122 Uttar Pradesh, India.
European Journal of Pharmacology
|November 16, 2002
Summary
Mibefradil effectively inhibits uterine contractions by blocking calcium channels and intracellular calcium release. This novel calcium channel antagonist shows potential as a tocolytic agent for managing preterm labor.
Area of Science:
- Pharmacology
- Cardiovascular Research
- Reproductive Physiology
Background:
- Mibefradil is a novel benzimidazolyl tetralol derivative and calcium (Ca2+) channel antagonist.
- It exhibits distinct structural properties compared to traditional antagonists like nifedipine, verapamil, and diltiazem.
- Mibefradil is recognized for its antihypertensive effects, primarily through blocking low-voltage-activated (T-type) Ca2+ channels, but also affects high-voltage-activated (L-type) channels.
Purpose of the Study:
- To investigate the effects of mibefradil on uterine contractility in pregnant and non-pregnant rats.
- To determine mibefradil's mechanism of action on spontaneous contractions, calcium chloride (CaCl2)-induced contractions, and oxytocin-induced contractions.
- To evaluate the potential of mibefradil as a tocolytic agent.
Main Methods:
- Uterus strips from pregnant and non-pregnant rats were used to assess spontaneous rhythmic contractions.
- Contractions were also elicited by CaCl2 in potassium (K+)-depolarized preparations and by oxytocin in low Ca2+/Ca2+-free solutions.
- Concentration-dependent effects of mibefradil were measured using IC50 values for amplitude and frequency, and shifts in concentration-response curves for CaCl2 and oxytocin.
Main Results:
- Mibefradil demonstrated a concentration-dependent inhibition of spontaneous uterine contractions in both pregnant and non-pregnant rats.
- It shifted the CaCl2 concentration-response curves rightward in K+-depolarized uterus strips, indicating L-type Ca2+ channel antagonism, with greater potency in pregnant rats.
- Mibefradil inhibited oxytocin-induced contractions in Ca2+-free solutions for pregnant rat uterus strips, suggesting interference with intracellular Ca2+ release mechanisms.
Conclusions:
- Mibefradil antagonizes L-type Ca2+ channels in rat uterine smooth muscle.
- It also appears to interfere with intracellular Ca2+ release mechanisms, particularly in pregnant uteri.
- These combined actions suggest mibefradil holds promise as a potential tocolytic agent for preventing premature uterine contractions.