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Preferential regulation of rabbit cardiac L‐type Ca 2+ current by glycolytic derived ATP via a direct allosteric pathway
Author(s) -
Losito Vito A.,
Tsushima Robert G.,
Diaz Roberto J.,
Wilson Gregory J.,
Backx Peter H.
Publication year - 1998
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1998.067bi.x
Subject(s) - glycolysis , chemistry , oxidative phosphorylation , intracellular , allosteric regulation , biophysics , intracellular ph , deoxyglucose , biochemistry , endocrinology , medicine , metabolism , biology , enzyme
1 The activity of Ca 2+ channels is regulated by a number of mechanisms including direct allosteric modulation by intracellular ATP. Since ATP derived from glycolysis is preferentially used for membrane function, we hypothesized that glycolytic ATP also preferentially regulates cardiac L‐type Ca 2+ channels. 2 To test this hypothesis, peak L‐type Ca 2+ currents (I Ca ) were measured in voltage‐clamped rabbit cardiomyocytes during glycolytic inhibition (2‐deoxyglucose + pyruvate), oxidative inhibition (cyanide + glucose) or both (full metabolic inhibition; FMI). 3 A 10 min period of FMI resulted in a 40·0 % decrease in peak I Ca at +10 mV (‐5·1 ± 0·6 versus ‐3·1 ± 0·4 pA pF −1 ; n = 5 , P < 0 ·01). Similar decreases in peak I Ca were observed during glycolytic inhibition using 2‐deoxyglucose (‐6·2 ± 0·2 versus ‐3·7 ± 0·2 pA pF −1 ; n = 5 , P < 0 ·01) or iodoacetamide (‐6·7 ± 0·3 versus ‐3·7 ± 0·2 pA pF −1 ; n = 7 , P < 0 ·01), but not following oxidative inhibition (‐6·2 ± 0·4 versus ‐6·4 ± 0·3 pA pF −1 ; n = 5 , n.s.). The reduction in I Ca following glycolytic inhibition was not mediated by phosphate sequestration by 2‐deoxyglucose or changes in intracellular pH. 4 Reductions in I Ca were still observed when inorganic phosphate and creatine were included in the pipette, confirming a critical role for glycolysis in I Ca regulation. 5 With 5 mM MgATP in the pipette during FMI, peak I Ca decreased by only 18·4 % (‐6·8 ± 0·6 versus ‐5·5 ± 0·3 pA pF −1 ; n = 4 , P < 0 ·05), while inclusion of 5 mM MgAMP‐PCP (β,γ‐methyleneadenosine 5′‐triphosphate, Mg 2+ salt) completely prevented the decrease in peak I Ca (‐6·9 ± 0·3 versus ‐6·5 ± 0·3 pA pF −1 ; n = 5 , n.s.). 6 Together, these results suggest that I Ca is regulated by intracellular ATP derived from glycolysis and does not require hydrolysis of ATP. This regulation is expected to be energy conserving during periods of metabolic stress and myocardial ischaemia.