A 90-kD Na(+)-H+ exchanger kinase has increased activity in spontaneously hypertensive rat vascular smooth muscle cells.
Increased activity of the Na(+)-H+ exchanger (NHE-1 isoform) has been observed in cells and tissues from hypertensive humans and animals, including the spontaneously hypertensive rat (SHR). No mutation in NHE-1 DNA sequence or alteration in NHE-1 mRNA and protein expression has been demonstrated in hypertension, indicating that alterations in proteins that regulate NHE-1 activity are responsible for increased activity. The recent finding that NHE-1 phosphorylation in SHR vascular smooth muscle cells (VSMCs) was greater than in Wistar-Kyoto rat (WKY) VSMCs suggested that NHE-1 kinases may represent an abnormal regulatory pathway present in hypertension. To define NHE-1 kinases altered in the hypertensive phenotype. We measured NHE-1 kinase activity by an in-gel-kinase assay using a recombinant glutathione S-transferase NHE-1 fusion protein as a substrate. At least 7 NHE-1 kinases (42 to 90 kD) were present in VSMCs. We studied a 90-kD kinase because it was the major NHE-1 kinase and exhibited differences between SHR and WKY. Comparison of 90-kD kinase activity revealed that SHR VSMCs had increased activity in growth-arrested cells and in cells stimulated by angiotensin II (100 nmol/L for 5 minutes). Activation of the 90-kD kinase by angiotensin II was Ca2+ dependent, PKC independent, and partially dependent on the mitogen-activated protein kinase pathway. These findings indicate that increased activity of a 90-kD NHE-1 kinase is a characteristic of SHR VSMCs in culture and suggest that alterations in the 90-kD NHE-1 kinase and/or proteins that regulate its activity may be a pathogenic component in hypertension in the SHR.
Phan
V N
VN
Department of Medicine, University of Washington, Seattle 98195, USA.
Kusuhara
M
M
Lucchesi
P A
PA
Berk
B C
BC
D000818:Animals; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000201:enzymology* / Q000378:metabolism; D010770:Phosphotransferases / Q000378:metabolism*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D013045:Species Specificity
D004791:Enzyme Inhibitors; D005419:Flavonoids; D017923:Sodium-Hydrogen Exchangers; D010770:Phosphotransferases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one