A 90-kD Na+-H+Exchanger Kinase Has Increased Activity in Spontaneously Hypertensive Rat Vascular Smooth Muscle Cells
作者:
Van N. Phan,
Masatoshi Kusuhara,
Pamela A. Lucchesi,
Bradford C. Berk,
期刊:
Hypertension
(OVID Available online 1997)
卷期:
Volume 29,
issue 6
页码: 1265-1272
ISSN:0194-911X
年代: 1997
出版商: OVID
数据来源: OVID
摘要:
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. (Hypertension. 1997;29:1265-1272.)
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