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Chronic hypoxia and postnatal maturation alter isoform expression and specific activity of protein kinase G in ovine carotid arteries
Author(s) -
Williams James M,
Pearce William J
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a1389
Subject(s) - medicine , endocrinology , hypoxia (environmental) , blot , gene isoform , cgmp dependent protein kinase , chemistry , enzyme , biology , protein kinase a , biochemistry , organic chemistry , oxygen , gene , cyclin dependent kinase 2
In ovine carotid arteries, relaxation responses to 8pCPT‐cGMP, a cell permeant non‐hydrolyzable analogue of cGMP, are strongly influenced by chronic hypoxia and postnatal maturation. Measurement of 8‐pCPT‐cGMP activated PKG enzyme activity by phosphate transfer of ATP[γ 32 P] to a specific PKG substrate (BPDEtide) was significantly depressed by postnatal maturation. To test the hypothesis that the expression of PKG determines enzyme activity and is regulated by maturation and chronic hypoxia, the relative abundances of PKG isoforms were assessed using specific antibodies. Quantitative Western blots revealed that relative total PKG abundances were markedly greater in fetal than adult arteries under both normoxic (A: 1.11 ± 0.11, F: 1.47 ± 0.21) and hypoxic (A: 1.09 ± 0.06, F: 1.51 ± 0.23) conditions. Normalizing PKG enzyme activity by relative abundance indicated no significant differences between groups and ranged between 1196 ± 174 and 1320 ± 186 pmol Pi/min/unit PKG. Owing that PKG exists in two isoforms, quantitative Western blots using isoform specific antibodies were used to examine both PKG Iα and PKG Iβ abundances. Relative abundances for PKG Iα was not significantly different between groups and ranged between 1.03 ± 0.11 and 1.20 ± 0.10. In contrast, PKG Iβ abundances were significantly depressed by postnatal maturation in both normoxic (A: 1.51 ± 0.07, F: 2.30 ± 0.19) and hypoxic (A: 1.50 ± 0.14, F: 1.90 ± 0.14) arteries. These differences suggest that PKG Iβ is physiologically downregulated by maturation. Such changes have important implications for vascular regulation and reactivity to NO in fetuses born following conditions of chronic intrauterine hypoxia and/or fetal distress. Supported by NIH HD31226, HL54120, and HL64867.