Effects of Sodium Restriction on Renin, Norepinephrine, and Cation Content of Cardiovascular Tissues of Dogs

Seven dogs were maintained for 1 month on a severely sodium-restricted diet. Another group of 4 dogs was maintained on the same dietary regimen with the addition of a “normal” NaCl supplement and served as controls. We studied: (a) renin activity in plasma (PRA). renal cortex (RRA), saphenous and mesenteric arteries (2nd to 5th branches), aorta, and left ventricle; (b) norepinephrine (NE) content of branches of mesenteric and saphenous arteries and veins, aorta, and left ventricle; (c) cation and water contents in saphenous, mesenteric (2nd to 5th branches), carotid and renal arteries, aorta, and left ventricle; (d) juxtaglomerular granulation index (JGI); (e) glucose-6-phosphate dehydrogenase (G6PD) activity in the cells of the adrenal zona glomerulosa. The most important findings were: (i) a significant increase of PRA and RRA and a slight, although not significant, increase in renin activity in the vascular tissues studied; (ii) a constant, but not significant, decrease in norepinephrine content in the same tissues; (iii) an unaltered plasma sodium concentration; (iv) a significant decrease of sodium content in all vascular tissues studied, with the exception of the renal artery; and (v) a significant increase in JGI associated with a greater G6PD activity in the adrenal zona glomerulosa.