1. Aldosterone given acutely to male Wistar rats stimulated ouabain-sensitive and ouabain-insensitive 22Na efflux from tail arteries.
2. These effects of aldosterone seem to depend on the activation of specific mineralocorticoid receptors, as they are blocked by antimineralo-corticoid drugs.
3. The results suggest that aldosterone may have a physiological role in the control of vascular tone.