Increased aldosterone secretion by tumor-bearing rats

¹ National Cancer Institute and National Heart Institute, National Institutes of Health, Bethesda, Maryland

Sprague-Dawley rats, bearing the Walker carcinosarcoma 256 subcutaneously, retain more of their daily sodium intake than do normal (nontumor-bearing) growing rats. In the present study, secretion of aldosterone and corticosterone has been determined in 16 such tumor-bearing rats and in 8 normal controls. The left renal vein was cannulated and effluent blood from the left adrenal collected. Blood flow rate and hematocrit were measured. Aldosterone and corticosterone were determined in the collected plasma by the double-isotope derivative method. Aldosterone secretion rate and concentration in effluent plasma, effluent plasma flow rate, adrenal size, and width of the zona glomerulosa were all significantly higher in the tumor-bearing group than in the normal. Aldosterone secretion rate was elevated 250%. Corticosterone secretion rate and concentration in plasma were not significantly different in the two groups. These results, in which a tumor provides the primary stimulus for sodium retention, are similar to results reported by others in sodium-deficient rats. A similar mechanism for sodium control is probably operative in both cases.