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NJBMS - Volume 5, Issue 1, July - September 2014

Pages: 21-24
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INTERDEPENDENCE OF THE CALCIUM RELEASE CHANNELS ON THE SARCOPLASMIC RETICULUM IN FROG VENTRICLE

Author: P. SATHYAVATHI

Category: Physiology

Abstract:

Background and objectives: Calcium is the prime mediator of the contractile mechanism in frog ventricle. Sarcoplasmic reticulum (SR) releases calcium by a well-known calcium induced calcium release (CICR) mechanism. CICR is mediated by ryanodine receptor (RyR) and inositol 1,4, 5- triphosphate (IP3) receptors on the SR membrane. This increase in cytosolic calcium concentration causes contraction of the cardiac muscle. Aim :The study aims at examining the interdependent role of the known calcium release channels on the SR in frog ventricle.

Materials and Methods and the Study Design: Isolated ventricular strips of frogs (rana hexadactyla) were used for the study. The study design includes subjecting the ventricular strip to continuous electrical stimulation with imposed rest periods intermittently to examine the diastolic depletion of calcium from the SR. The magnitude of decay of the post rest amplitude in relation to the pre rest amplitude was analyzed following each rest period in two independent sets of experiments using neomycin and ryanodine. Neomycin inhibits the formation of IP3 and ryanodine is a blocker of RyR Qualitative analysis of calcium was done, considering the contractile force of the tissue as an indicator of the concentration of calcium. Statistical significance was assessed by two way analysis of variance.

Results and conclusion: The results show that during diastole, after blocking these known SR calcium release channels independently, calcium depletion persisted indicating that their release mechanism is independent of each other.

Keywords: Calcium, Inositol1, 4, 5- triphosphate, Neomycin, Ryanodine, Sarcoplasmic reticulum