Mechanism of preservation of myocardial calcium channel function by pyruvate cardioplegic solution.
We evaluated the effects of adding pyruvate to a cardioplegic solution on the preservation of the dihydropyridine-sensitive calcium (Ca2+) current responses to beta-adrenergic stimulation in rabbit cardiac myocytes by measurement of single-channel open probability. Single ventricular myocytes were isolated and stored in St. Thomas' solution with or without pyruvate at 4 degrees C for 2, 6, 12, or 24 hours, and cell-attached single Ca2+ channel currents recordings were made at 20 degrees to 22 degrees C after each storage period. When 0.1 micromol/L isoproterenol (ISO) was applied to the cells, the percent mean open probability of the Ca2+ channels tested in freshly isolated cells was 181% +/- 27% (n = 12) of control values. These responses decreased with an increasing duration of the hypothermic storage and were only 112% +/- 22% (n = 5) of control values after 24 hours of storage in the absence of pyruvate. Conversely, the responses were significantly preserved, to as much as 143% +/- 17% (n = 7), in the presence of 10 mmol/L pyruvate in the storage solution. The application of forskolin to stimulate adenylate cyclase or a membrane-permeable cyclic adenosine monophosphate mimicked the effects of ISO when the myocytes were stored with pyruvate. Pyruvate did not alter the open-channel kinetics or single-channel conductance and lacked any apparent direct effect on the Ca2+ channel activity. We suggest that pyruvate added to the hypothermic storage solution preserves the high-energy phosphates in myocytes that are responsible for Ca2+ channel phosphorylation via beta-adrenergic stimulation. (J Lab
Ono
K
K
Department of Physiology, Oita Medical University, Japan.
Wada
T
T
Lee
T S
TS
Gondo
N
N
Hadama
T
T
Arita
M
M
D000818:Animals; D015220:Calcium Channels / Q000502:physiology*; D002314:Cardioplegic Solutions; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D007035:Hypothermia; D066298:In Vitro Techniques; D007700:Kinetics; D009206:Myocardium / Q000201:enzymology; D010766:Phosphorylation; D011773:Pyruvates / Q000008:administration & dosage / Q000494:pharmacology*; D011817:Rabbits
D015220:Calcium Channels; D002314:Cardioplegic Solutions; D011773:Pyruvates; D005576:Colforsin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases