Functional role of the soluble guanylyl cyclase alpha(1) subunit in vascular smooth muscle relaxation.
OBJECTIVE
Soluble guanylyl cyclase (sGC), the predominant receptor for nitric oxide (NO), exists in 2 active isoforms (alpha(2)beta(1) and alpha(1)beta(1)). In vascular tissue sGCalpha(1)beta(1) is believed to be the most important. The aim of our study was to investigate the functional importance of the sGCalpha(1)-subunit in vasorelaxation.


METHODS
Aortic and femoral artery segments from male and/or female sGCalpha(1)(-/-) mice and wild-type littermates were mounted in a small-vessel myograph for isometric tension recording. This was supplemented with biochemical measurements of the cGMP concentration and sGC enzyme activity.


RESULTS
The functional importance of sGCalpha(1)beta(1) was demonstrated by the significantly decreased relaxing effects of acetylcholine (ACh), sodium nitroprusside (SNP), S-nitroso-N-acetylpenicillamine (SNAP), NO gas, YC-1, BAY 41-2272 and T-1032 in the sGCalpha(1)(-/-) mice of both genders. Moreover, the basal and SNP-stimulated cGMP levels and basal sGC activity were significantly lower in the sGCalpha(1)(-/-) mice. However, the relaxing effects of NO, BAY 41-2272 and YC-1 seen in blood vessels from sGCalpha(1)(-/-) mice indicate a role for an sGCalpha(1)beta(1)-independent mechanism. The increase in sGC activity after addition of BAY 41-2272 and the inhibition of the ACh-, SNP-, SNAP- and NO gas-induced response by the sGC inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) in the sGCalpha(1)(-/-) mice are observations suggesting that the sGCalpha(2)beta(1) isoform is also functionally active. However, the insignificant increase in cGMP in response to SNP and the non-upregulated sGCalpha(2) expression level in the sGCalpha(1)(-/-) mice suggest rather the involvement of (an) sGC-independent mechanism(s).


CONCLUSIONS
We conclude that sGCalpha(1)beta(1) is involved in the vasorelaxation induced by NO-dependent and NO-independent sGC activators in both genders. However, the remaining relaxation seen in the sGCalpha(1)(-/-) mice suggests that besides sGCalpha(1)beta(1) also the minor isoform sGCalpha(2)beta(1) and/or (an) sGC-independent mechanism(s) play(s) a substantial role.
Nimmegeers
Sofie
S
Department of Physiology and Physiopathology, Ghent University, Ghent, Belgium.
Sips
Patrick
P
Buys
Emmanuel
E
Brouckaert
Peter
P
Van de Voorde
Johan
J
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001011:Aorta; D006152:Cyclic GMP / Q000032:analysis / Q000378:metabolism; D005260:Female; D006162:Guanylate Cyclase / Q000032:analysis / Q000037:antagonists & inhibitors / Q000502:physiology*; D066298:In Vitro Techniques; D007191:Indazoles / Q000494:pharmacology; D007527:Isoenzymes / Q000502:physiology*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D018160:Receptors, Cytoplasmic and Nuclear / Q000032:analysis / Q000037:antagonists & inhibitors / Q000502:physiology*; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology; D000071756:Soluble Guanylyl Cyclase; D014665:Vasodilator Agents / Q000494:pharmacology
C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; C423582:3-(4-Amino-5-cyclopropylpyrimidine-2-yl)-1-(2-fluorobenzyl)-1H-pyrazolo(3,4-b)pyridine; C000605665:Gucy1a2 protein, mouse; D007191:Indazoles; D007527:Isoenzymes; D020030:Nitric Oxide Donors; D010069:Oxadiazoles; D011720:Pyrazoles; D011725:Pyridines; D011810:Quinoxalines; D018160:Receptors, Cytoplasmic and Nuclear; D014665:Vasodilator Agents; C090937:3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole; D009599:Nitroprusside; D009569:Nitric Oxide; D026423:S-Nitroso-N-Acetylpenicillamine; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase; D006152:Cyclic GMP; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester