Alteration of voltage-dependent calcium channels in canine brain during global ischemia and reperfusion.
Elevated intracellular calcium (iCa2+) plays an important role in the pathophysiology of ischemic brain damage. The mechanisms by which iCa2+ increases are uncertain. Recent evidence implicates the voltage-dependent calcium channel (VDCC) as a likely site for the alteration in Ca2+ homeostasis during ischemia. The purpose of this study was to determine whether VDCCs are altered by global ischemia and reperfusion in a canine cardiac arrest, resuscitation model. We employed the radioligand, [3H]PN200-110, to quantitate the equilibrium binding characteristics of the VDCCs in the cerebral cortex. Twenty-five adult beagles were separated into four experimental groups: (a) nonischemic controls, (b) those undergoing 10-min ventricular fibrillation and apnea, (c) those undergoing 10-min ventricular fibrillation and apnea followed by spontaneous circulation and controlled respiration for 2 and (d) 24 h. Brain cortex samples were taken prior to killing of the animal, frozen immediately in liquid nitrogen, and crude synaptosomal membranes isolated by differential centrifugation/filtration. After 10 min of ischemia the maximal binding (Bmax) of [3H]PN200-110 increased to greater than 250% of control values (control Bmax 11.16 +/- 0.98; ischemic 28.35 +/- 2.78 fmol/mg protein; p less than 0.05). Bmax returned to near control values after 2 h of reperfusion but remained significantly greater than the control at 24 h. Although the affinity constant (Kd) (control = 0.12 +/- 0.03 nM) appeared to increase with ischemia and normalize with reperfusion, the changes were not statistically significant. We conclude that the binding of [3H]PN200-110 to L-type VDCCs is increased after 10 min of global ischemia/anoxia produced by ventricular fibrillation and apnea in the dog.(ABSTRACT TRUNCATED AT 250 WORDS)
Hoehner
P J
PJ
Department of Anesthesiology and Critical Care Medicine, Johns Hopkins Medical Institutions, Baltimore, MD.
Blanck
T J
TJ
Roy
R
R
Rosenthal
R E
RE
Fiskum
G
G
D000818:Animals; D001665:Binding Sites; D002545:Brain Ischemia / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D004095:Dihydropyridines / Q000494:pharmacology; D004285:Dogs; D005260:Female; D017275:Isradipine; D009568:Nitrendipine / Q000378:metabolism; D015424:Reperfusion; D013574:Synaptosomes / Q000378:metabolism
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004095:Dihydropyridines; D009568:Nitrendipine; D017275:Isradipine