Ionophore mediated equilibration of calcium ion gradients in fragmented-sarcoplasmic reticulum

Kinetics of calcium transport by fragmented sarcoplasmic reticulum.

Calcium transport by sarcotubular vesicles (fragmented sarcoplasmic reticulum) from skeletal muscle of rats, rabbits, and humans follows Michaelis-Menten kinetics when studied in systems containing oxalate and low ratios of calcium to vesicle protein. Under these conditions different preparations of vesicles are characterized by their calcium concentrating ability, i.e. the constant level to wh...

The Effect of Calcium Ionophores on Fragmented Sarcoplasmic Reticulum

X-537 A and A 23187, two antibiotics which form liphophilic complexes with divalent cations, function as ionophores in vesicular fragments of sarcoplasmic reticulum (SR). Addition of either ionophore to SR preloaded with calcium in the presence of adenosine triphosphate (ATP), causes rapid release of calcium. Furthermore, net calcium accumulation by SR is prevented, when the ionophores are adde...

Dependence of ionophore- and caffeine-induced calcium release from sarcoplasmic reticulum vesicles on external and internal calcium ion concentrations.

The effects of the ionophore, X537A, and caffeine on ATP-dependent calcium transport by fragmented sarcoplasmic reticulum were studied in the absence (calcium storage) or presence (calcium uptake) of calcium-precipitating anions. The ionophore caused rapid calcium release after calcium storage, the final level of calcium storage being the same whether a given concentration of X537A was added pr...

Ion pumping by calcium ATPase of sarcoplasmic reticulum.

Illuminating sarcoplasmic reticulum calcium.

The bulk of the Ca 2 that activates contraction in the heart comes from the sarcoplasmic reticulum (SR). Calcium is released by the process of Ca -induced Ca release (CICR) in which the entry of a small amount of Ca across the cell membrane triggers the release of much more from the SR. This mechanism depends on the fact that Ca entry from the extracellular fluid (via the L-type Ca current) inc...