H. Fukuda et al., The effect of K-ATP channel activation on myocardial cationic and energetic status during ischemia and reperfusion: Role in cardioprotection, J MOL CEL C, 33(3), 2001, pp. 545-560
The role of cation and cellular energy homeostasis in ATP-sensitive K-1 (K-
APP) channel-induced cardioprotection is poorly understood. To evaluate thi
s, rapidly interleaved Na-23 and P-31 NMR spectra were acquired from isolat
ed rat hearts exposed to direct Na-i(+) channel activation from nicorandil
or pinacidil. Nicorandil attenuated ATP depiction and intracellular Na+ (Na
-i(+)) accumulation, delayed the progression of acidosis during zero-flow i
schemia and prevented ischemic contracture. The Na-i(+) channel inhibitor 5
-hydroxydecanoate abolished these effects. Pinacidil did not alter Na-i(+),
accumulation, ATF depletion or pH during ischemia under the conditions emp
loyed. Both agonists greatly improved the post-ischemic functional recovery
. Both agonists also dramatically improved tl-re rate and extent of the rep
erfusion recoveries of Na-i(+) PCr and ATP. The Na-i(+) and PCr reperfusion
recovery rates were tightly correlated, suggesting a causal relationship.
Separate atomic absorption tissue Ca2+ measurements revealed a marked reper
fusion Ca2+ uptake, which was reduced two-fold by pinacidil. In conclusion,
these results clearly indicate that while K-ATP channel-induced metabolic
alterations carl vary the functional cardioprotection resulting from this f
orm of pharmacological preconditioning does not require atenuation of acido
sis, cellular energy depletion, or Na-i(+) accumulation during ischemia. Ra
ther than preservation of cationic/energetic status during ischemia, the ca
rdioprotective processes may involve a preserved capability for its rapid r
estoration during reperfusion. The enhanced reperfusion Na-i(+) recovery ma
p be enabled by the improved reperfusion cellular energy state. This accele
rated Na-i(+) recovery could play an important cardioprotective role via a
potential causal relationship with the reduction of reperfusion tissue Ca2 uptake and resultant reperfusion injury. (C) 2001 Academic Press.