RESUMO
The properties of the Na/K pump and Na,K,Cl cotransporter were studied in vascular tissue of two-kidney Goldblatt hypertensive rats. These transport systems were measured as ouabain-sensitive and bumetanide-sensitive 86Rb/K uptake in aortic rings, left ventricular muscle and soleus skeletal muscle fibers of control and hypertensive Sprague-Dawley rats. A dramatic increment in Na/K pump activity was observed in intact aortic rings from the hypertensive group. The same was true for the Na,K,Cl cotransporter. The transport parameters related to the left ventricular muscle and soleus skeletal muscle were not significantly altered in the hypertensive rats. Measurements of the catalytic isoforms of the Na+, K(+)-ATPase in the aortic rings indicated that both isoforms (alpha 1 and alpha 2) were elevated in the same proportion in the hypertensive rats. The results also indicate that the endothelium plays an important role in both transport systems: in the absence of endothelium, a much lower 86Rb/K uptake was observed than in intact aortic rings, either from control or hypertensive vascular tissue. Nevertheless, when the 86Rb/K transport activity was measured in denuded aortic rings, a significantly higher ouabain and bumetanide sensitive 86Rb/K uptake was also observed in the hypertensive rats. These data also show no alteration in the endothelium of the hypertensive rats as compared to control animals. The presence of endothelium had a more striking effect on the alpha 2 catalytic isoform activity than on the alpha 1 isoform. We conclude that there is a significant increment in the Na/K pump and Na,K,Cl cotransporter in two kidney-Goldblatt hypertension, that is specific for vascular smooth muscle.
