NJBMS - Volume 4, Issue 3, January - March 2014

Pages: 173-176




Category: Physiology

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Background and Objectives: In amphibian ventricle, steady loss of calcium occurs during diastole. Sodium calcium exchanger (NCX) clears calcium to the exterior causing rhythm generation. Calcium loss was demonstrated by decrease in the contractile force after an imposed rest period‑rest induced decay (RID). Calcium channel blockers with anti‑arrhythmic activity cause increase in contractile force following a rest period (rest induced potentiation), which could be due to reversal of NCX. Hence other therapeutically used anti‑arrhythmic agents may also influence the working direction of NCX.

Materials and Methods: Frog ventricular strips when electrically stimulated in solution resembling extracellular fluid show a steady state of contraction. Different classes of anti‑arrhythmic agents according to Vaugan William’s classification belonging to classes Ia, Ib, III and IV were examined for reversal of NCX. Rest periods were imposed in between contraction, ranging from 20 to 100 and 180 s and similar protocol was followed with the drug of intervention on the same tissue. The post rest and pre rest amplitudes of contraction were compared and analysed.

Results: RID that was observed with the control solution did not get converted into potentiation with any of the above mentioned classes of anti‑arrhythmic agents.

Interpretation and Conclusion: Unlike the results observed with calcium channel blockers verapamil and diltiazem, no reversal in the direction of the working mode of NCX was noted with the above said anti‑arrhythmic agents as shown by the persistence of RID. Hence these anti‑arrhythmic agents do not influence the working mode of NCX in their anti‑arrhythmic action.

Keywords: Anti‑arrhythmic, Calcium, Sodium calcium exchanger, Rest induced decay, Rest induced potentiation

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Editor in Chief of NJBMS Dr.Deepti Shastri, Professor and Head, Department of Anatomy, Academic Co-ordinator for Pre and Paraclinical Sciences, VMKV Medical College & Hospital, Salem.

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