Decreased Na⁺K⁺ATPase Activity in the Aortic Endothelium and Smooth Muscle of the Spontaneously Hypertensive Rats

The activity of Na+K+ ATPase in the endothelium and smooth muscle of the aortae of normotensive and hypertensive rats was investigated. The enzyme activity in the endothelium and smooth muscle of the spontaneously hypertensive rats (SHR) was 2.15 +/- 0.48 and 12.98 +/- 0.99 respectively. These values were significantly lower (P less than 0.05) than the enzyme activity in the corresponding tissues (10.10 +/- 1.78 for endothelium, 20.77 +/- 2.54 for smooth muscle) of the normotensive Wistar Kyoto (WKY) rats. However, with the low blood pressure spontaneously hypertensive rats (LBP-SHR) i.e. in those animals whose blood pressures were below 150 mm Hg, the enzyme activity in both tissues was not significantly different from those of the WKY. Since Na+ K+ ATPase is coupled to the sodium-potassium pump whose activity affects the functions of other pumps, the results indicate that the development of high blood pressure in the SHR may be related to an alteration in the transport of cations across the cell membrane.