Preconditioning cultured human pediatric myocytes requires adenosine and protein kinase C

We showed previously that 20 min of low-volume anoxia ("ischemia") and 20 min of "reperfusion" preconditions quiescent pediatric myocyte cultures against damage resulting from 90 min of subsequent prolonged ischemia and 30 min of reperfusion. The purpose of this study was to assess the roles of adenosine and protein kinase C (PKC) in this preconditioning model. Our results suggest that 1) preconditioned myocytes secrete a protective mediator(s) into the "ischemic" supernatant that is transferable to other cells, and adenosine is released into the supernatant in quantities sufficient for adenosine-receptor activation (2) preconditioning is inhibited by adenosine-receptor antagonism, and myocyte protection similar to preconditioning can be achieved with exogenously administered adenosine or adenosine-receptor stimulation; (3) brief ischemic and adenosine-induced myocyte preconditioning is mimicked by the phorbol ester 4beta-phorbol 12-myristate 13-acetate (PKC agonist) and inhibited by PKC antagonists; and (4) brief ischemic and adenosine-induced myocyte preconditioning both induce PKC translocation to myocyte membranes and increase the PKC phosphorylation rate. These data suggest that adenosine released from ischemic human pediatric myocytes mediates preconditioning through activation of PKC.

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Synergism between phorbol ester and the Ca2+ ionophore A23187 on protein kinase C translocation, [3H]PDBu binding and adenosine A2-receptor activation in Jurkat cells

European Journal of Pharmacology Molecular Pharmacology ◽

10.1016/0922-4106(90)90195-4 ◽

1990 ◽

Vol 188 (6) ◽

pp. 349-357 ◽

Cited By ~ 2

Author(s):

Christer Nordstedt

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Phorbol Ester ◽

Receptor Activation ◽

Jurkat Cells ◽

Ionophore A23187 ◽

Kinase C ◽

Adenosine A2 Receptor ◽

Pdbu Binding

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Adenosine-induced activation of ATP-sensitive K+ channels in excised membrane patches is mediated by PKC

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1999.276.2.h488 ◽

1999 ◽

Vol 276 (2) ◽

pp. H488-H495 ◽

Cited By ~ 10

Author(s):

Keli Hu ◽

Gui-Rong Li ◽

Stanley Nattel

Keyword(s):

Protein Kinase C ◽

Adenosine Receptor ◽

Receptor Activation ◽

Channel Activity ◽

Pipette Solution ◽

K Channels ◽

Adenosine Receptor Antagonist ◽

Kinase C ◽

Adenosine Receptor Activation ◽

Pkc Activation

Both protein kinase C (PKC) and adenosine receptor activation have been shown to enhance ATP-sensitive K+(KATP) channels. The present studies were designed to determine whether PKC mediates adenosine effects on the KATP channel. The dependence of KATP channel activity ( nP o) on intracellular ATP concentration ([ATP]i) was determined in excised rabbit ventricular membrane patches. External adenosine (100 μM in the pipette solution) significantly increased KATP nP o at all [ATP]i between 5 and 50 μM by decreasing channel sensitivity to [ATP]i (dissociation constant increased from 7.4 ± 0.8 to 22.2 ± 3.1 μM, P < 0.001), an effect blocked by the adenosine receptor antagonist 8-phenyltheophylline (10 μM). When the highly selective PKC blocker bisindolylmaleimide (BIM) was included in the internal (bath) solution, the KATP-stimulating action of adenosine was prevented. The addition of BIM to the superfusate rapidly inhibited KATP channels activated by adenosine. Endogenous PKC activation by phorbol 12,13-didecanoate (PDD), but not administration of the inactive congener 4α-PDD, enhanced KATP activity. Internal guanosine 5′- O-(2-thiodiphosphate) prevented KATP activation by adenosine, an effect which could be overridden by exposure to PDD. We conclude that PKC mediates adenosine activation of KATP channels in excised membrane patches in a membrane-delimited fashion.

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