through a decrease in AA content in cell membranes, potenti-

ation of the protective function of eNOS and modulation of

iNOS-derived NO release after ischemia/reperfusion.

doi:10.1016/j.yjmcc.2006.03.134

120. Regulation of cell survival by KATP channels:

Sarcolemmal, mitochondrial or both?

Aleksandar Jovanovic. Maternal and Child Health Sciences,

Ninewells Hospital and Medical School, University of Dundee,

Dundee DD1 9SY, UK

Sarcolemmal and mitochondrial ATP-sensitive K+ (KATP)

channels have been described by Noma, 1983, Nature, 305:

147–148 and Inoue et al., 1991, Nature 352: 244–247,

respectively. While the structure of sarcolemmal KATP (sKATP)

channels is well established, the structure of mitochondrial

KATP (mKATP) channels is controversial to such extend that

even their existence is questioned. Consequently, different

researchers hold very different views about roles that sKATP

and mKATP channels might play in cardioprotective signalling.

In our laboratory, we have found that an increase in number of

sKATP channels confers cellular phenotype resistant to hypoxia/

ischaemia and that preconditioning is associated with the

recruitment and activation of sKATP channels. The channel activa-

tion and consequent shortening of the action membrane potential

seem to be important for cell survival in hypoxia/ischaemia.

Our experience with mKATP channels is not as extensive as

with sKATP channels. However, we have found that precondi-

tioning in single beating cardiomyocytes was associated with

mitochondrial membrane depolarisation, which would be in

accord with the activation of K+ conductance in mitochondrial

membrane. The signalling cascade mediating preconditioning-

induced mitochondrial membrane depolarisation involves

phosphoinositide-dependent kinase-1, protein kinase B and

glycogen synthase kinase-3h. This cascade seems to be

distinctive from the one that regulate sKATP channels in

preconditioning, which involves AMP-activated protein kinase.

At the present stage of our knowledge, it is probably fair to

say that sKATP channels are involved in cardioprotective

signalling, while more research is needed in the future before

strong conclusions could be made about the role of mKATP

channels in cardioprotection.

doi:10.1016/j.yjmcc.2006.03.135

121. NECA given at reperfusion limits infarction and

inhibits formation of the mitochondrial permeability

transition pore by activating p70S6 kinase

K. Foerster, I. Paul, T. Krieg. Department of Cardiology,

Ernst-Moritz-Arndt University Greifswald, Germany

The A1/A2 adenosine agonist 5V-(N-ethylcarboxamido)

adenosine (NECA) limits myocardial infarction when adminis-

tered at reperfusion.We tested whether p70S6 kinase is involved

in this cardioprotective effect. Adult rat ventricular myocytes

were loaded with TMRE (100 nM) which causes cells to

fluoresce in proportion to their mitochondrial membrane

potential (Cm). A reduction of fluorescence serves as an

indicator of collapse of Cm, and, presumably to permeability

transition pore (mPTP) formation. Cells were subjected to H2O2

(200 AM) which causes mPTP formation. Cm was considered

as irreversibly collapsed when fluorescence reached less than

60% of the starting value. Treatment with NECA (1 mM)

delayed the collapse ofCm (48.0 T 3.2 min vs. 29.5 T 2.2 min in

untreated cells, P < 0.01), and that protection was blocked with

the co-administration of the mTOR/p70S6 inhibitor rapamycin

(5 nM). Inhibition of GSK-3h has been proposed to be the

downstream suppressor of mPTP formation. The GSK-3hinhibitor SB216763 (3 AM) also prolonged the time to collapse

of Cm (49.2 T 2.1 min, P < 0.01). This protection was

unaffected by rapamycin suggesting that GSK-3h resides

downstream of p70S6. NECA treatment (100 nM) of isolated

rabbit hearts at reperfusion after 30 min of regional ischemia

decreased infarct size from 33.0 T 3.8% of the risk zone in

control hearts to 11.8 T 2.0% (P < 0.001), and rapamycin

blocked this protection. A comparable effect was seen for

SB216763 (1 AM) with infarct size reduction to 13.5 T 2.3%

(P < 0.001). In summary, these experiments reveal a critical role

for p70S6 upstream of mPTP in the signaling pathway of

NECA’s cardioprotection at reperfusion.

doi:10.1016/j.yjmcc.2006.03.136

122. Endogenous hydrogen sulfide contributes to the

cardioprotective effects of pre-conditioning with

endotoxin, but not ischaemia, in the rat

A. Sivarajah, M.C. McDonald, C. Thiemermann. William

Harvey Research Institute, Centre for Experimental Medicine,

Nephrology and Critical Care, UK

Gasotransmitters are endogenous gases of small molecular

weight, which exert important physiological functions. Their

production and metabolism are enzymatically regulated, and

their effects are not dependent on specific membrane receptors.

In recent years, another naturally occurring gas, hydrogen sul-

fide (H2S), has been found to be of importance. Here we

investigate whether the cardioprotective effects of pre-condi-

tioning (PC) with endotoxin (LPS) or ischaemia are due to en-

dogenous hydrogen sulfide (H2S). In male Wistar rats, two

cycles (5 min) of PC with ischaemia followed by regional myo-

cardial ischaemia–reperfusion resulted in a significant reduction

(50%) in infarct size. When compared to vehicle-treated

animals, 16 h pre-treatment with LPS (1 mg/kg i.p.) resulted in

a significant reduction (41%) in infarct size. Administration of

the irreversible cystathionine-g-lyase inhibitor, dl-propargyl-

glycine (PAG, 50 mg/kg), which prevents the formation of H2S,

did not affect the cardioprotective effect afforded by ischaemic

PC, but abolished the cardioprotective effects afforded by LPS.

Administration of 5-hydroxydecanoate (5 mg/kg) also abolished

the cardioprotective effect of LPS. These findings demonstrate

ABSTRACTS / Journal of Molecular and Cellular Cardiology 40 (2006) 920–1015964