Comparison of ouabain-sensitive 86Rb uptake of canine renal and femoral arteries

Abstract

We have previously reported that various manifestations of the Na+ pump, such as ouabain binding, Na+-K+-ATPase, and 86Rb uptake, were similar in canine renal and femoral arteries [R.D. Bukoski, C.L. Seidel, and J.C. Allen. Am. J. Physiol. 245 (Heart Circ. Physiol. 14): H604-H609, 1983.]. In this report we compare ouabain-sensitive 86Rb uptake in renal and femoral arteries under two selected conditions of intracellular Na+:low Na+ and Na+ loaded. When intracellular Na+ was low, the renal artery dissociation constant for Rb+ was 1.13 mM compared with the Na+-loaded condition of 2.49 mM. The femoral artery dissociation constant remained the same at both Na+ levels. The maximal rate of 86Rb uptake (Vmax) of the renal artery was the same at both Na+ levels, but the femoral artery Vmax was 23.6 and 11.11 nmol X mg-1 X 20 min-1 in Na+-loaded and low-Na+ vessels, respectively. The reason for the difference in Na+ pump regulation in these two vessels is not clear, but these results suggest that there are heterogeneous mechanisms for controlling ionic movements in vascular smooth muscle.