NS309 restores EDHF-type relaxation in mesenteric small arteries from type 2 diabetic ZDF rats.
OBJECTIVE
The endothelium-derived hyperpolarizing factor (EDHF)-type relaxation in mesenteric small arteries from 21 week old Zucker lean (ZL) and Zucker diabetic fatty (ZDF) rats was investigated using (6,7-dichloro-1H-indole-2,3-dione 3-oxime) (NS309), a potent activator of small-conductance, calcium-activated potassium channel (SK(Ca)) and intermediate-conductance, calcium-activated potassium channel (IK(Ca)).


METHODS
In the presence of inhibitors of cyclooxygenase and nitric oxide synthase [indomethacin and N(omega)-nitro-L-arginine methyl ester (l-NAME), respectively], acetylcholine (ACh)-induced hyperpolarization and EDHF-type relaxation were investigated under isometric conditions in the wire myograph using 0.5 and 1 microM NS309 and/or selective blockers of SK(Ca) and IK(Ca) channels. Membrane potential was recorded with glass microelectrodes, and changes in the intracellular calcium concentration of endothelial cells were visualized by confocal microscopy. SK(Ca) expression was assessed by Western blotting.


RESULTS
In arteries from ZDF rats, ACh-induced relaxation and membrane hyperpolarization were attenuated and, compared with arteries from ZL rats, NS309 was less potent at causing relaxation. Incubation with 0.5 microM NS309 did not increase ACh-induced relaxation in arteries from ZDF rats significantly. However, 1 microM NS309 restored it (both in the absence and in the presence of indomethacin and l-NAME) without changing endothelial intracellular calcium concentration. The restored EDHF-type relaxation was more sensitive to TRAM-34 (1-[(2-chlorophenyl) diphenylmethyl]-1H-pyrazole) (1 microM) than to apamin. Expression of the SK(Ca) channel was unaltered.


CONCLUSIONS
The attenuated EDHF-type relaxation in mesenteric small arteries from ZDF rats can be restored by NS309 without changes in the intracellular calcium concentration of endothelial cells. These results may have clinical implications for the treatment of endothelial dysfunction in overweight type 2 diabetic patients.
Brøndum
E
E
The Water and Salt Research Center, Institute of Physiology and Biophysics, Aarhus University, DK-8000 Aarhus C, Denmark.
Kold-Petersen
H
H
Simonsen
U
U
Aalkjaer
Christian
C
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001685:Biological Factors / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D004305:Dose-Response Relationship, Drug; D007211:Indoles / Q000008:administration & dosage / Q000494:pharmacology*; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008638:Mesenteric Arteries / Q000187:drug effects / Q000378:metabolism; D010091:Oximes / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D011924:Rats, Zucker; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000187:drug effects / Q000378:metabolism
C493327:6,7-dichloro-1H-indole-2,3-dione 3-oxime; D001685:Biological Factors; D007211:Indoles; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; D010091:Oximes; D051640:Small-Conductance Calcium-Activated Potassium Channels; C067410:endothelium-dependent hyperpolarization factor; D000109:Acetylcholine; D002118:Calcium