Tocolytic effect of calcium channel blockers on buffalo uterus

Abstract

A study was conducted to evaluate the tocolytic effect of selective calcium channel blockers on uterine strips of buffaloes. Prostaglandin F2 alpha (PGF2α), oxytocin, (OT), potassium chloride (CK1) and barium chloride (BaCl2) were used to induce uterine contractions of pregnant and diestrous stage buffaloes. After contracting the tissues, cumulative concentration-response curves of verapamil and diltiazem were constructed and their mean effective concentration (EC50) values were determined and statistically compared. Comparative EC50 values of CCBs revealed the rank order potency of PGF2α> KC1> BaCl2> OT on pregnant uteri while OT > PGF2α > KC1 > BaCl2 on dioestrus animals uteri for verapamil. The rank order potency of diltiazem was different from that of verapamil and it was KCl > OT > PGF2α > BaCl2 on pregnant while KCl > PGF2α > BaCl2 > OT on dioestrus stage uteri. Difference in the rank order potency of verapamil and diltiazem against different spasmogens on the uteri of pregnant or dioestrus stage buffaloes may be attributed to the difference in chemical structure of verapamil and diltiazem or their binding with calcium channels or due to difference in the molecular mechanism of different spasmogens-induced contraction. Further, it may not be unreasonable to state that CCBs appear to be promising tocolytics for buffaloes, however, detailed in-vivo pharmacological studies are warranted to estiablish their clinical utility and safety in farm animals including buffaloes.