Related Experiment Video
Updated: Oct 11, 2026

Optical Mapping of Intra-Sarcoplasmic Reticulum Ca2+ and Transmembrane Potential in the Langendorff-perfused Rabbit Heart
Published on: September 10, 2015
Is a functional sarcoplasmic reticulum necessary for preconditioning?
1Division of Radiological Sciences, 5th floor, Thomas Guy House, Guy's Hospital, London, UK. alison.cave@kcl.ac.uk
Abstract:
Several studies have shown that the protective effect of ischemic preconditioning (PC) is associated with decreased calcium release from the sarcoplasmic reticulum (SR). However, no study has yet demonstrated whether these changes are essential in the mechanism of PC. In order to investigate whether a functional SR was necessary for PC, we manipulated SR calcium handling using (i) 0.1microM ryanodine (RY), a concentration known to lock the SR calcium release channel in the open state and (ii) 50microM cyclopiazonic acid (CPA), a specific inhibitor of the SR calcium ATPase. Initial experiments confirmed that both RY and CPA eliminated the ability of the SR to accumulate calcium. Isolated rat hearts (n=6-7/group) were perfused normoxically for 30 min prior to either a further 40 min of perfusion [control (C)] or 4x[5 min ischemia (I) + 5 min reperfusion (R)] (PC). All hearts were then subjected to a further 40 min I + 40 min R. The C and PC protocols were then repeated in the presence of RY or CPA, introduced after 10 min of perfusion.(31)P-NMR was used to measure ATP, PCr, P(i)and intracellular pH. RY and CPA decreased developed pressure (DP) by 75% and 59%, respectively. Percentage recovery of LVDP was significantly higher in PC (72+/-8%), PC+RY (72+/-7%) and PC+CPA (49+/-7%) groups compared with their respective controls (43+/-7%, 47+/-7% and 10+/-4%) (P<0.05). Thus, PC remains protective in the presence of a SR unable to accumulate calcium, suggesting that the changes in SR calcium release are not essential in the mechanism of preconditioning.
More Related Videos
Related Concept Videos
Endoplasmic Reticulum
Overview of Skeletal Muscle
Microscopic Anatomy of Skeletal Muscles
The muscle sarcolemma is a plasma membrane enclosing each muscle cell that conducts electrical signals called action potentials. The sarcolemma extends into the cell to form T-tubules, ensuring the neural impulses are uniformly distributed across the entire muscle...
The Sarcomere
Each myosin...
Relaxation of Skeletal Muscles
When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated sodium channels. Sodium ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated calcium channels to open.
Smooth Muscle Contraction
The onset of contraction is triggered by an increase in calcium ions within the sarcoplasm, similar to the process in striated muscle. However, smooth muscles have a relatively smaller reservoir of the sarcoplasmic...

