Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.3.1 (Mg2+-ATPase)
 1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ruthenium red inhibited Ca2+-ATPase and ATP-independent Ca2+ binding with rat heart sarcolemma in a concentration dependent manner; significant effects were evident at 0.25 microM and higher concentrations. The apparent Ka for Ca2+-ATPase was 1.02 +/- 0.02 mM Ca2+ and 1.47 +/- 0.12 mM Ca2+ in the absence and presence of 2.5 microM ruthenium red, respectively; however, no change in the Vmax (41.2 +/- 1.6 mumol Pi/mg/h) was observed. Likewise, the affinity of Ca2+ for both low and high affinity Ca2+ binding sites in sarcolemma was decreased by ruthenium red. Sarcolemmal Na+-dependent Ca2+ uptake, ATP-dependent Ca2+ accumulation, Mg2+-ATPase and Na+,K+-ATPase activities were not affected by ruthenium red. In sarcoplasmic reticulum preparations, ruthenium red (0.25 to 25 microM) enhanced Ca2+ uptake without altering the Ca2+-stimulated ATPase activity. The observed increase in Ca2+ uptake appears to be due to the depressant effect of the dye on Ca2+ release from the sarcoplasmic reticulum. In mitochondrial preparations, ruthenium red (0.025 to 25 microM) showed a marked inhibitory effect on Ca2+ uptake activity whereas the Mg2+-ATPase activity was unaltered. In isolated rat hearts, 0.025 microM ruthenium red produced a slight negative inotropic effect, whereas 0.25 to 2.5 microM ruthenium red elicited a biphasic response both in terms of developed tension and resting tension. High concentrations of ruthenium red (12.5 to 25 microM) resulted in the development of contracture. Electron microscopic studies revealed the presence of ruthenium red in the myoplasm of hearts perfused for 15 to 30 mins with 2.5 to 5 microM dye.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Influence of ruthenium red on rat heart subcellular calcium transport. 246 13

Tryptic modification appears to potentiate activation of the Ca2+ channels of isolated sarcoplasmic reticulum vesicles. In the presence of 1 mM free Mg2+ we observe that: 1) cAMP and doxorubicin activation of passive efflux from tryptically modified vesicles is approximately 20-fold greater than from native SR. 2) Ruthenium red inhibits Ca2+ efflux from modified vesicles. 3) The binding affinities and Hill coefficients of activation of efflux by cAMP and doxorubicin are the same in modified vesicles as in native vesicles. 4) Proteolysis stimulates passive efflux from heavy SR much more than from light SR. 5) Stimulation of cAMP- and doxorubicin-activated Ca2+ release is biphasic, whereas Hg2+-activated Ca2+ efflux is monophasic. 6) In the absence of Mg2+, the Ca2+ dependence of cAMP-activated efflux from tryptically modified vesicles is similar to that of native vesicles, with peak efflux rates occurring between approximately 1 and 10 microM Ca2+. 7) The Mg2+ dependence of efflux from modified vesicles is similar to that of native vesicles. 8) SDS-polyacrylamide gels indicate that the Ca2+, Mg2+-ATPase and the high molecular weight ryanodine receptor are both cleaved faster than the stimulation of efflux.
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PMID:Limited tryptic modification stimulates activation of Ca2+ release from isolated sarcoplasmic reticulum vesicles. 284 65