BACKGROUND: cGMP-dependent protein kinase type I (PKG I) plays a key role in vasodilatation caused by cGMP-elevating agents. It is a homodimer in mammalian cells, existing as 2 isoforms, Iα and Iβ. The aim of the present study was both to determine whether PKG I dimerization and activity are modulated by hydrogen peroxide (H(2)O(2)) and its influence on vasodilatation. METHODS AND RESULTS: The dimers and monomers of total PKG I and PKG Iβ were analyzed by Western blotting. PKG I activity was assayed by measuring the incorporation of (32)P into BPDEtide. Changes in vessels tension were determined by organ chamber technique. In isolated porcine coronary arteries, H(2)O(2) increased the dimers of total PKG I in a concentration-dependent manner, but had no effect on dimerization of PKG Iβ. The dimerization of PKG I caused by H(2)O(2) was prevented by catalase but not by deferoxamine and tiron. H(2)O(2) promoted the translocation of PKG I from cytoplasm to membrane. H(2)O(2) enhanced the activity of PKG I and relaxations of porcine coronary arteries to the nitric oxide donor and 8-Br-cGMP. Inhibition of catalase under in vivo conditions significantly decreased rat mean arterial pressure, which was associated with increased dimerization of PKG I. CONCLUSIONS: The present study suggests that H(2)O(2) may enhance the activity of PKG Iα-and PKG I-dependent vasodilatation via increased dimerization of the enzyme.
BACKGROUND:cGMP-dependent protein kinase type I (PKG I) plays a key role in vasodilatation caused by cGMP-elevating agents. It is a homodimer in mammalian cells, existing as 2 isoforms, Iα and Iβ. The aim of the present study was both to determine whether PKG I dimerization and activity are modulated by hydrogen peroxide (H(2)O(2)) and its influence on vasodilatation. METHODS AND RESULTS: The dimers and monomers of total PKG I and PKG Iβ were analyzed by Western blotting. PKG I activity was assayed by measuring the incorporation of (32)P into BPDEtide. Changes in vessels tension were determined by organ chamber technique. In isolated porcine coronary arteries, H(2)O(2) increased the dimers of total PKG I in a concentration-dependent manner, but had no effect on dimerization of PKG Iβ. The dimerization of PKG I caused by H(2)O(2) was prevented by catalase but not by deferoxamine and tiron. H(2)O(2) promoted the translocation of PKG I from cytoplasm to membrane. H(2)O(2) enhanced the activity of PKG I and relaxations of porcine coronary arteries to the nitric oxidedonor and 8-Br-cGMP. Inhibition of catalase under in vivo conditions significantly decreased rat mean arterial pressure, which was associated with increased dimerization of PKG I. CONCLUSIONS: The present study suggests that H(2)O(2) may enhance the activity of PKG Iα-and PKG I-dependent vasodilatation via increased dimerization of the enzyme.