Mm. Mocanu et al., Glimepiride, a novel sulfonylurea, does not abolish myocardial protection afforded by either ischemic preconditioning or diazoxide, CIRCULATION, 103(25), 2001, pp. 3111-3116
Citations number
27
Categorie Soggetti
Cardiovascular & Respiratory Systems","Cardiovascular & Hematology Research
Background-The sulfonylurea glibenclamide (Glib) abolishes the cardioprotec
tive effect of ischemic preconditioning (IP), presumably by inhibiting mito
chondrial K-ATP channel opening in myocytes. Glimepiride (Glim) is a new su
lfonylurea reported to affect nonpancreatic K-ATP channels less than does G
lib. We examined the effects of Glim on IP and on the protection afforded b
y diazoxide (Diaz), an opener of mitochondrial K-ATP channels.
Methods and Results-Rat hearts were Langendorff-perfused, subjected to 35 m
inutes of regional ischemia and 120 minutes of reperfusion, and assigned to
1 of the following treatment groups: (1) control; (2) IP of 2X 5 minutes e
ach of global ischemia before lethal ischemia, or pretreatment with (3) 30
mu mol/L Diaz, (4) 10 mu mol/L Glim. (5) 10 mu mol/L Glib, (6) IP+Glim, (7)
IP+Glib, (8) Diaz+Glim, or (9) Diaz+Glib. IP limited infarct size (18.5 +/
-1% vs 43.7 +/-3% in control, P<0.01) as did Diaz (22.2<plus/minus>4.7%. P<
0.01), The protective actions of IP or Diaz were not abolished by Glim (18.
5<plus/minus>3% in IP+Glim, 22.3 +/-3% in Diaz+Glim; P<0.01 vs control). Ho
wever, Glib abolished the infarct-limiting effects of IP and Diaz, Patch-cl
amp studies in isolated rat ventricular myocytes confirmed that both Glim a
nd Glib teach at 1 <mu>mol/L blocked sarcolemmal K-ATP currents. However, i
n isolated cardiac mitochondria, Glim(10 mu mol/L) failed to block the effe
cts of K-ATP opening by GTP, in contrast to the blockade caused by Glib.
Conclusions-Although it blocks sarcolemmal currents in rat cardiac myocytes
. Glim does not block the beneficial effects of mitochondrial K-ATP channel
opening in the isolated rat heart. These data may have significant implica
tions for the treatment of type 2 diabetes in patients with ongoing ischemi
c heart disease.