Ryanodine and an iodinated analog: doxorubicin effects on binding and Ca2+ accumulation in cardiac sarcoplasmic reticulum
| Autor: | Dale E. Mais, August M. Watanabe, Koert Gerzon, Nancy Bowling |
|---|---|
| Rok vydání: | 1994 |
| Předmět: |
medicine.medical_specialty
animal structures chemistry.chemical_element Calcium Biology In Vitro Techniques Ligands Iodine Radioisotopes Radioligand Assay Dogs Internal medicine Microsomes medicine Animals Doxorubicin Pharmacology Ryanodine receptor Ryanodine Endoplasmic reticulum Vesicle Calcium Radioisotopes Myocardium Heart Sarcoplasmic Reticulum Endocrinology Mechanism of action chemistry Microsome Liberation medicine.symptom medicine.drug |
| Zdroj: | European journal of pharmacology. 268(3) |
| ISSN: | 0014-2999 |
| Popis: | An 125I-iodinated ryanodine analog, modified by attaching an iodo-Cbz-β-alanyl group to the C10eq hydroxy of ryanodine (iodo-carbobenzyloxy-β-alanyl-ryanodine), binds to cardiac sarcoplasmic reticulum Ca2+ release channels with equal affinity as [3H]ryanodine. In the present study, both iodo-Cbz-β-alanyl-ryanodine and ryanodine bound to canine cardiac microsomal membrane preparations in a Ca2+ dependent manner. At 10 μM free Ca2+ doxorubicin increased specific binding of both ligands, with doxorubicin concentrations of 4.06 ± 0.44 and 6.22 ± 1.31 μM inducing 50% maximal enhancement of binding for ryanodine and iodo-Cbz-β-alanyl-ryanodine, respectively. Effects of ryanodine and iodo-Cbz-β-alanyl-ryanodine ± doxorubicin in vitro on cardiac sarcoplasmic reticulum Ca2+ release were compared indirectly by determining Ca2+ accumulation in cardiac microsomal vesicles loaded with 45Ca2+. In the absence of oxalate, neither ryanodine nor iodo-Cbz-β-alanyl-ryanodine (10 μM) decreased net Ca2+ uptake, whereas doxorubicin reduced Ca2+ accumulation 20 ± 2%. In the presence of oxalate and 0.4 μM free Ca2+ (“low”), both ryanodine and iodo-Cbz-β-alanyl-ryanodine modestly decreased (by 19% and 17% at 10 nM, respectively) maximum Ca2+ accumulation. Increasing concentrations of ryanodine (100 nM-100 μM) and iodo-Cbz-β-alanyl-ryanodine (100 nM-30 μM) had no greater effect, but 100 μM iodo-Cbz-β-alanyl-ryanodine decreased net Ca2+ uptake 57 ± 3% Doxorubicin (30 μM) alone reduced Ca2+ uptake 36%; its effects with 1 nM–10 μM ryanodine or 1 nM–100 μM iodol-Cbz-β-alanyl-ryanodine were additive. In the presence of oxalate and 4.0 μM free Ca2+ (“high”), 10–100 μM ryanodine resulted in 27–91% concentration-dependent increases in net Ca2+ uptake. In contrast, iodo-Cbz-β-alanyl-ryanodine (10–100 μM) had no effect. Doxorubicin (30 μM), alone or in the presence of iodo-Cbz-β-alanyl-ryanodine, reduced Ca2+ uptake less than 10%, but it decreased by 25% the maximal enhancement of Ca2+ uptake by ryanodine. We conclude that ryanodine and iodo-Cbz-β-alanyl-ryanodine have similar binding properties, but their effects on cardiac sarcoplasmic reticulum Ca2+ accumulation may reflect differing actions on the sarcoplasmic reticulum Ca2+ efflux channels. |
| Databáze: | OpenAIRE |
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