Mechanism of action of "ruthenium red" compounds on Ca2+ ionophore from sarcoplasmic reticulum (Ca2+ + Mg2+)- adenosine triphosphatase and lipid bilayer

Interaction of ruthenium red with Ca2(+)-binding proteins

The interaction of ruthenium red, [(NH3)5Ru-O-Ru(NH3)4-O-Ru(NH3)5]Cl6.4H2O, with various Ca2(+)-binding proteins was studied. Ruthenium red inhibited Ca2+ binding to the sarcoplasmic reticulum protein, calsequestrin, immobilized on Sepharose 4B. Furthermore, ruthenium red bound to calsequestrin with high affinity (Kd = 0.7 microM; Bmax = 218 nmol/mg protein). The dye stained calsequestrin in sodium dodecyl sulfate-polyacrylamide gels or on nitrocellulose paper and was displaced by Ca2+ (Ki = 1.4 mM). The specificity of ruthenium red staining of several Ca2(+)-binding proteins was investigated by comparison with two other detection methods, 45Ca2+ autoradiography and the Stains-all reaction. Ruthenium red bound to the same proteins detected by the 45Ca2+ overlay technique. Ruthenium red stained both the erythrocyte Band 3 anion transporter and the Ca2(+)-ATPase of skeletal muscle sarcoplasmic reticulum. Ruthenium red also stained the EF hand conformation Ca2(+)-binding proteins, calmodulin, troponin C, and S-100. This inorganic dye provides a simple, rapid method for detecting various types of Ca2(+)-binding proteins following electrophoresis.

The role of mitochondria and sarcoplasmic reticulum calcium handling upon reoxygenation of hypoxic myocardium

The mechanism of twitch prolongation of hypoxic myocardium after reoxygenation was studied before and after interventions that affect cellular cyclic nucleotide levels, subcellular calcium handling, or oxygen-derived free radical production/survival. Right ventricular ferret papillary muscles were subjected to two 20-minute periods of hypoxia, each followed by 1 hour of reoxygenation. The first sequence of hypoxia/reoxygenation was done without intervention. Before the second sequence, the pharmacological agent under study was added to the superfusate or the superfusate calcium concentration was increased from 2.5 to 8 mM. Time from peak to 80% decline in twitch tension was measured in the presence and absence of each intervention immediately before each period of hypoxia and after reoxygenation at maximal twitch prolongation. Interventions that affect Ca2+ flux across the sarcolemma (verapamil and 8 mM [Ca2+]o) or agents that affect oxygen free radical production/survival (dimethyl sulfoxide and allopurinol) did not affect twitch prolongation. Pharmacological agents that increase cyclic AMP levels (forskolin and milrinone) or those that inhibit mitochondrial activity (oligomycin B and ruthenium red) attenuated twitch prolongation. Pharmacological agents that decrease cyclic AMP levels (carbachol) or inhibit function of the sarcoplasmic reticulum (ryanodine) augmented twitch prolongation. The effect of mitochondrial inhibitors on intracellular calcium handling during hypoxia and reoxygenation was examined using muscles loaded with the bioluminescent calcium indicator aequorin. Mitochondrial inhibitors abbreviated the calcium transient and maximal twitch prolongation after hypoxia. We conclude that alterations in sarcoplasmic reticulum and mitochondria calcium handling contribute to the prolonged relaxation seen upon reoxygenation of hypoxic myocardium.

Effect of diamide on isolated guinea pig atria

Diamide [(diazinedicarboxylic acid-bis (dimethylamide)] 50 micrograms/ml induced a positive inotropic and chronotropic effect on spontaneously beating atria from normal and reserpine pretreated guinea pigs and a positive inotropic action on electrically driven left atria. Cumulative addition of diamide 600 micrograms/ml caused a systolic standstill of atria. D(-) INPEA 2 micrograms/ml, a beta-adrenergic blocking agent, antagonized the positive chronotropic action of diamide 50 micrograms/ml while it did not affect the positive inotropic action caused by diamide. In isolated atria perfused with Ca2+ free medium and recovered by stepwise addition of calcium chloride, the calcium level required to restore normal activity was 1.04 mmol/1 while it was 0.52 mmol/l in the presence of diamide. Ruthenium red 10 micrograms/ml, a specific inhibitor of calcium transport in mitochondria, antagonized diamide-induced recovery of the cardiac activity in calcium poor medium. Two different mechanisms, that involve calcium movements and beta-receptor, have been proposed for diamide action on heart muscle.

The interaction between ruthenium red and the isolated sarcoplasmic reticulum

The multivalent anions, ATP and oxalate, present at 5mM concentrations in incubation mixtures with isolated sarcoplasmic reticulum (SR) preparations, reduce the binding of ruthenium red (RR) to the SR. When oxalate is omitted from the incubation mixture and ATP is used at reduced concentrations, it is possible to observe an inhibitory effect of RR on calcium uptake by the SR and on ATPase activity. However, this inhibition is only partial and it remains clear that calcium transport in the SR is much less susceptible to inhibition by RR than is calcium transport in mitochondria. The effect of multivalent anions in suppressing the effect of RR, a hexavalent cation, is probably due to the formation of soluble complexes with RR.

Photosensory transduction in the flagellated alga, Euglena gracilis I. Action of divalent cations, Ca2+ antagonists and Ca2+ ionophore on motility and photobehavior

1. The flagellated alga, Euglena gracilis, swims forward essentially in a straight path under constant light intensity. Strong motility of the cells can be supported by Mg2+ alone but optimum motility is found in the presence of Mg2+, Ca2+ and K+. 2. Ca2+, Co2+, Mn2+ and Ba2+ induce a concentration-dependent increase in the rate at which the cells change the direction of their swimming path (a klinokinesis). Ni2+ immobilizes the flagellum. 3. On perception of a reduction ('step-down stimulus') in blue light intensity in their environment, Euglena rotate in place (tumble) for a finite period (the step-down photophobic response). 4. The duration of the tumbling is enhanced in the presence of divalent cations following the series Ca2+ greater than Ba2+ greater than Mn2+ greater than Co2+ greater than Mg2+ = Ni2+ = 0. 5. Neither the tumbling response in the presence of low concentrations of Ca2+ or the Ca2+-stimulated response is altered by verapamil (a Ca2+ conductance antagonist). The Ca2+ conductance/active transport antagonist, ruthenium red, is also inactive. 6. The Ca2+ ionophore, A23187, has little effect on flagellar activity in the absence of extracellular Ca2+. However, in the presence of A23187, Ca2+ induces a specific light-independent, concentration-dependent discontinuous tumbling response of the cells. 7. The data support a role for Ca2+ and Mg2+ in control of flagellar activity. However, blue light-induced tumbling behavior would not appear to be the direct result of a light-mediated alteration in the Ca2+ conductance of the flagellar membrane to affect flagellar reorientation. The results are discussed in connection with previous theories on control of flagella activity in green alga.

Physiological dissection of various effects of ruthenium red dye on Paramecium cells

Polycationic dye ruthenium red, but not alcian blue, if externally applied to Paramecium cells quickly inhibits their phagocytosis. Ruthenium red combined with the cell surface diminishes frequency and duration of ciliary reversals and gradually inactivates the Ca++ gating mechanism. This effect persists for 1-3 after ruthenium red removal from the culture medium.

(+)-alpha-(N-1-phenethyl) urea stereospecifically inhibits Ca2+ - but not ADP-stimulated mitochondrial respiration

The (+) isomer of alpha-(N-1-phenethyl) urea is a moderately potent inhibitor of Ca2+ -stimulated mitochondrial respiration of 45Ca2+ uptake (50 percent inhibition at 0.18 mM) while having no effect on adenosine diphosphate-stimulated respiration; the (-) isomer is without effect up to 4 mM. beta-Phenethylurea does not inhibit with either stimulus. The data support the involvement of a Ca2+ -specific protein in energized mitochondrial Ca2+ uptake.