[Chronic dietary sodium overload and release of a circulating Na+-K+ pump inhibitor]

High Na+ intake has been proposed to induce a rise in the activity of a circulating inhibitor of the Na+, K+-pump. The effects on male Wistar rats of a high sodium diet (8 per cent NaCl) on the activity of such a plasma Na+, K+-ATPase inhibitor were investigated. Systolic blood pressure, body weight, urinary Na+ excretion, haematocrit, intraerythrocytic Na+ content and the activity of a Na+ dependent transport system, i.e. the uptake of 5-HT by blood platelets were measured in parallel. After one week, neither systolic blood pressure nor intraerythrocytic Na+ content were modified, but the ability of the plasma extracts to inhibit renal Na+, K+-ATPase increased (70.9 +/- 1.7 vs 76.3 +/- 2.1 mumol Pi/mg/h; p = 0.05). After two weeks, the plasma inhibitory activity, the systolic blood pressure and the intraerythrocytic Na+ content were higher than that of control animals (65.5 +/- 1.6 vs 79.1 +/- 2.8 mumol Pi/mg/h, p less than 0.001; 132 +/- 2 vs 114 +/- 4 mmHg, p. +/- 0.001 and 4.95 +/- 0.32 vs 3.81 +/- 0.36 mmol/l.cells, p less than 0.05). After three months, the ability of plasma extracts to inhibit the Na+ pump and the systolic blood pressure were still elevated (57.8 +/- 1.8 vs 72.9 +/- 1.8 mumol Pi/mg/h, p less than 0.001; 145 +/- 4 vs 118 +/- 2 mmHg, p less than 0.001) whereas intraerythrocytic Na+ content had returned to control levels and 5-HT uptake was not modified.(ABSTRACT TRUNCATED AT 250 WORDS)