title: Mitochondrial and cytosolic calcium in rat hearts under high-K(+) cardioplegia and pyruvate: mechano-energetic performance.
abstract: High-K(+)-cardioplegia (CPG) and pyruvate (Pyr) are used as cardioprotective agents. Considering that mitochondria play a critical role in cardiac dysfunction, we investigated the effect of CPG on mitochondrial Ca(2+) uptake and sarcorreticular (SR) calcium handling. Cytosolic and mitochondrial Ca(2+), as well as mitochondrial membrane potential (ΔΨm) were assessed in rat cardiomyocytes by confocal microscopy. Mechano-calorimetrical correlation was studied in perfused hearts. CPG did not modify JC-1 (ΔΨm), but transiently increased, by up to 1.8 times, the Fura-2 (intracellular Ca concentration, [Ca(2+)]i) and Rhod-2 (mitochondrial free Ca concentration [Ca(2+)]m) fluorescence of resting cells, with exponential decays. The addition of 5 µmol·L(-1) thapsigargin (Tpg) increased the Rhod-2 fluorescence in a group of cells without any effect on the Fura-2 signal. In rat hearts perfused with CPG, 1 µmol·L(-1) Tpg decreased resting heat rate (ΔH(r): -0.44 ± 0.07 mW·g(-1)), while the addition of 5 µmol·L(-1) KB-R7943 increased resting pressure (ΔrLVP by +5.26 ± 1.10 mm Hg; 1 mm Hg = 133.322 Pa). The addition of 10 mmol·L(-1) Pyr to CPG increased H(r) (+3.30 ± 0.24 mW·g(-1)) and ΔrLVP (+2.2 ± 0.4 mm Hg), which are effects potentiated by KB-R7943. The results suggest that under CPG, (i) there was an increase in [Ca(2+)]i and [Ca(2+)]m (without changing ΔΨm) that decayed by exothermic removal mechanisms; (ii) mitochondrial Ca(2+) uptake contributed to the removal of cytosolic Ca(2+), in a process that was potentiated by inhibition of sarco-endoplasmic reticulum Ca(2+)-ATPase (SERCA), and reduced by KB-R7943; (iii) under these conditions, SERCA represents the main energetic consumer; (iv) Pyr increased the energetic performance of hearts,mainly by inducing mitochondrial metabolism.
authors.affiliation: Cátedra de Farmacología, Dept. Ciencias Biológicas, Universidad Nacional de La Plata (UNLP), Argentina. dinamia@biol.unlp.edu.ar
authors.forename: A E
authors.initials: AE
authors.lastname: Consolini
authors.forename: M I
authors.initials: MI
authors.lastname: Ragone
authors.forename: P
authors.initials: P
authors.lastname: Bonazzola
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000493:pharmacokinetics; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism*; D016257:Fura-2 / Q000378:metabolism; D006321:Heart / Q000187:drug effects; D006324:Heart Arrest, Induced / Q000379:methods*; D006575:Heterocyclic Compounds, 3-Ring / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D011188:Potassium / Q000008:administration & dosage; D019289:Pyruvic Acid / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology; D013890:Thiourea / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: C101670:2-(2-(4-(4-nitrobenzyloxy)phenyl)ethyl)isothiourea methanesulfonate; D006575:Heterocyclic Compounds, 3-Ring; C068483:rhod-2; D019284:Thapsigargin; D019289:Pyruvic Acid; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D013890:Thiourea; D011188:Potassium; D002118:Calcium; D016257:Fura-2