Reduced Sodium-Potassium Dependent Atpase and its Possible Role in the Development of Hypertension in Spontaneously Hypertensive Rats

Abstract

Ouabain-sensitive Na+-K+-ATPase activity in red cell membranes, kidney cortical tissue, myocardium and adrenal glomerulosa tissue was examined in SHR and WKY rats at 6, 9, and 12 weeks of age. Red cell membrane enzyme activity was decreased (p> 0.001) at 9 and 12 weeks of age in SHR. This activity was negatively correlated (r= -0.69, p>.005) with blood pressure at 9 and 12 weeks. Kidney cortical enzyme activity was also decreased (p> 0.001) in the SHR at 9 and 12 weeks of age. This decreased kidney enzyme activity was also inversely related to 9 and 12 week blood pressures (r= -0.71, p> 0.001), urinary Na excretion (r= -0.62, p>.005), and urinary Ca and K excretion. Myocardial enzyme activity was not decreased until 12 weeks in the SHR, and adrenal glomerulosa activity was not different in the SHR and WKY at any of the three ages that this enzyme was measured. Of the tissues examined decreased Na+-K+-ATPase activity in the erythrocyte membrane and in kidney cortical tissue appears to coincide best with the development of hypertension in the SHR. This study lends further support to the concept that alterations in membrane cation transport may be an important factor in the development of high blood pressure in SHR.

Key Words:

• SHR
• Na⁺-K⁺ ATPase