Procaine in cardioplegia: the effect on EDHF-mediated function in porcine coronary arteries.
OBJECTIVE
Hyperkalemia in cardioplegia impairs the endothelium-derived hyperpolarizing factor (EDHF)-mediated function. This study examined the effect of procaine in cardioplegia on the EDHF-mediated response in porcine coronary arteries.


METHODS
An isometric force study was performed in a myograph. Two rings taken from the same artery (diameter 200-450 microm) were incubated with Krebs solution (group I) or 20 mM K+ (group II) with/without procaine (1 mM) at 37 degrees C for 1 hour. The EDHF-mediated relaxation was induced by bradykinin (BK, -10 approximately -6.5 log M) after U46619 (-8 log M, in group I) or K+-precontraction (in group II) in the presence of indomethacin (7 microM), NG-nitro-L-arginine (300 microM), and hemoglobin (20 microM). The membrane potential of a single smooth muscle cell was measured by a microelectrode after superfusion with Krebs solution with/without procaine for 1 hour.


RESULTS
The EDHF-mediated relaxation was increased by the treatment with procaine with the EC50 shifted leftward (97.3 +/- 0.6% vs. 83.0 +/- 5.1% at -7 log M and 99.4 +/- 0.6% vs. 96.7 +/- 1.6% at -6.5 log M, p < 0.05; EC50: -8.57 +/- 0.24 vs. -7.92 +/- 0.23 log M, p < 0.05). Procaine decreased the BK-induced hyperpolarization from -72.3 +/- 0.7 mV to -68.8 +/- 0.8 mV (-6.5 log M, p < 0.01). The EDHF-mediated relaxation in arteries exposed to 20 mM K+ was not altered by procaine (49.9 +/- 7.4% vs. 55.8 +/- 7.6%, p > 0.05).


CONCLUSIONS
In the coronary arteries, procaine has a depolarizing effect but it enhances EDHF-mediated relaxation. Addition of procaine in cardioplegia did not change the EDHF-mediated endothelial function.
Yang
Qin
Q
Division of Cardiothoracic Surgery, Department of Surgery, The Chinese University of Hong Kong, Hong Kong SAR, China..
Yim
Anthony P C
AP
Arifi
Ahmed A
AA
He
Guo-Wei
GW
D000465:Algorithms; D000779:Anesthetics, Local / Q000494:pharmacology*; D000818:Animals; D001639:Bicarbonates; D001685:Biological Factors / Q000502:physiology*; D002122:Calcium Chloride; D002314:Cardioplegic Solutions; D003196:Computer Graphics; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology; D006324:Heart Arrest, Induced; D008274:Magnesium; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D023421:Models, Animal; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D011189:Potassium Chloride; D011343:Procaine / Q000494:pharmacology*; D012965:Sodium Chloride; D013552:Swine
D000779:Anesthetics, Local; D001639:Bicarbonates; D001685:Biological Factors; D002314:Cardioplegic Solutions; C041711:St. Thomas' Hospital cardioplegic solution; C067410:endothelium-dependent hyperpolarization factor; D012965:Sodium Chloride; D011343:Procaine; D011189:Potassium Chloride; D008274:Magnesium; D002122:Calcium Chloride