The goal of this study was to assess the role of the electrogenic Na+-K+ pump in controlling active tone in cremasteric arterioles of normotensive hamsters and hamsters with bilateral (two-kidney, two figure-8) Grollman hypertension. Arterioles of both groups exhibited a large transient dilation when the Na+-K+ pump was stimulated by superfusing the cremaster muscle with physiological salt solution containing 15 mM K+ after 20 minutes of 0 mM K+ superfusion. Arteriolar dilation in response to 15 mM K+ was significantly smaller in the hypertensive animals than in sham-operated controls. Ouabain (10(-5) M and 10(-3) M) inhibited arteriolar dilation in response to 15 mM K+ in both groups of animals. Resting diameters, total active tone (assessed by application of 10(-4) M adenosine), and arteriolar responses to inhibition of the Na+-K+ pump by superfusion with 0 mM K+ or ouabain were not significantly different in normotensive and hypertensive animals. These data indicate that an electrogenic Na+-K+ pump can regulate active tone in cremasteric arterioles, and that the maximum response of this pump to stimulation with 15 mM K+ is reduced in arterioles of hamsters with two-kidney Grollman hypertension.