Mw. Gorman et al., INORGANIC-PHOSPHATE AS REGULATOR OF ADENOSINE FORMATION IN ISOLATED GUINEA-PIG HEARTS, American journal of physiology. Heart and circulatory physiology, 41(2), 1997, pp. 913-920
This study evaluated cytosolic P-i as an independent regulator of card
iac adenosine formation by dissociating changes in P-i from changes in
AMP and ADP. Myocardial high-energy phosphates (HEP), measured by P-3
1 nuclear magnetic resonance spectroscopy, were depleted acutely by pe
rfusing isolated guinea pig hearts with 2-deoxyglucose (2-DG), and the
effects of 2-DG were compared with a norepinephrine infusion producin
g similar changes in HEP. 2-DG treatment resulted in lower adenosine r
elease (R(ado)) (54 +/- 18 vs. 622 +/- 199 pmol . min(-1). g(-1)) and
P-i concentration ([P-i]) (0.5 +/- 0.1 vs. 6.0 +/- 0.9 mM) than norepi
nephrine despite similar AMP concentration ([AMP]). Chronic phosphocre
atine depletion produced by beta-guanidinopropionic acid feeding also
reduced R(ado) and P-i during hypoxia. Replacement of perfusate glucos
e and pyruvate with acetate increased R(ado) (from 39 +/- 12 to 356 +/
- 100 pmol . min(-1). g(-1)) and [P-i] (from 2.0 +/- 0.5 to 5.1 +/- 0.
6 mM) with no change in cytosolic [AMP]. Adenosine kinase isolated fro
m guinea pig hearts was inhibited by [P-i] values seen during hypoxia
or hypoperfusion. We conclude that cytosolic [P-i] can be an important
regulator of cardiac adenosine formation through inhibition of adenos
ine kinase.