A 90-kD Na+ -H+ Exchanger Kinase Has Increased Activity in Spontaneously Hypertensive Rat Vascular Smooth Muscle Cells

• Published in: Hypertension (Dallas, Tex. 1979) Tex. 1979), 1997-06, Vol.29 (6), p.1265-1272
• Main Authors: Phan, Van N, Kusuhara, Masatoshi, Lucchesi, Pamela A, Berk, Bradford C
• Format: Article
• Language: English
• Subjects: Animals; Arterial hypertension. Arterial hypotension; Biological and medical sciences; Blood and lymphatic vessels; Cardiology. Vascular system; Down-Regulation; Enzyme Inhibitors - pharmacology; Experimental diseases; Flavonoids - pharmacology; Male; Medical sciences; Muscle, Smooth, Vascular - enzymology; Muscle, Smooth, Vascular - metabolism; Phosphotransferases - metabolism; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Sodium-Hydrogen Exchangers - metabolism; Species Specificity
• ISSN: 0194-911X; 1524-4563
• DOI: 10.1161/01.hyp.29.6.1265

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 Ca 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.)