The superiority of pinacidil over adenosine cardioplegia in blood-perfused isolated hearts.
BACKGROUND
Our laboratory has shown that the potassium-channel opener pinacidil is an effective cardioplegic agent. A theoretical benefit of cardioplegia with potassium-channel openers is that it arrests the heart at hyperpolarized membrane potentials, a state of minimal metabolic requirement. This study was designed to examine another nondepolarizing agent, adenosine, and to test the hypothesis that it could provide comparable cardioprotection or augment potassium-channel opener cardioplegia.


METHODS
Using the blood-perfused Langendorff technique, isolated rabbit hearts were arrested for 30 minutes of global normothermic ischemia. Cardioplegia consisted of either Krebs-Henseleit solution alone (control) or with pinacidil (50 micromol/L), adenosine (200 micromol/L to 1 mmol/ L), or pinacidil + adenosine (200 micromol/L). Recovery of developed pressure and coronary flow were recorded.


RESULTS
Postischemic functional recovery for control, pinacidil, adenosine, and adenosine + pinacidil groups was 44.1%+/-3.4%, 59.5%+/-5.2% (p < 0.05 versus control), 37.0%+/-4.5%, and 56.0%+/-2.9%, respectively.


CONCLUSIONS
Adenosine, alone or as adjunct to pinacidil cardioplegia, was not an effective cardioplegic agent, despite shorter times to electromechanical arrest than control. The ineffectiveness of adenosine suggests that the cardioprotective properties of potassium-channel openers involve mechanisms other than the avoidance of membrane depolarization.
Jayawant
A M
AM
Department of Surgery, Medical College of Virginia, Richmond, USA.
Damiano
R J
RJ
D000241:Adenosine / Q000494:pharmacology*; D000818:Animals; D001769:Blood; D002314:Cardioplegic Solutions / Q000737:chemistry / Q000494:pharmacology*; D005260:Female; D005947:Glucose / Q000737:chemistry / Q000494:pharmacology; D006321:Heart / Q000187:drug effects*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control; D010477:Perfusion; D020110:Pinacidil / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects; D011817:Rabbits; D014325:Tromethamine / Q000737:chemistry / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology*
D002314:Cardioplegic Solutions; C074097:Krebs-Henseleit solution; D015221:Potassium Channels; D014665:Vasodilator Agents; D014325:Tromethamine; D020110:Pinacidil; D005947:Glucose; D000241:Adenosine