Dietary sodium stimulates ouabainlike activity in adrenalectomized spontaneously hypertensive rats

Both the adrenal glands and the hypothalamus have been proposed to produce compound(s) with ouabainlike activity (OLA). To evaluate the contribution of the adrenal glands, 4-wk-old spontaneously hypertensive rats (SHR) were sham operated or adrenalectomized. The adrenalectomized SHR were given daily injections of corticosterone and aldosterone. Subsequently, rats were randomized to control or high (8%) dietary Na+, and after 2.5 wk, blood pressure and OLA in plasma, hypothalamus, and pituitary were evaluated. Hypertension developed somewhat less in adrenalectomized vs. sham-operated SHR. On control Na+ intake, adrenalectomy caused only minor decreases in circulating and central OLA. Adrenalectomy did not prevent the 50-90% increases in plasma, hypothalamus, and pituitary OLA caused by high Na+ intake for 2.5 wk. These findings are consistent with the concept that, at least in SHR, the central nervous system may represent the major source of both central and peripheral OLA.