A comparison of the haemodynamic effects of dietary sodium restriction and acute sodium depletion in the conscious sheep.

The use of a low Na, low K sorghum grain diet supplemented with intraruminal electrolyte infusions has enabled dietary manipulation of sodium status to be studied in the sheep. Dietary sodium restriction reduced urinary sodium excretion within 24 h with maximal retention after 3 days. There were no other substantial metabolic or haemodynamic changes. A more severe form of sodium deficiency produced by parotid salivary drainage resulted after only 2 days in a sodium deficit 3-4 times that seen with 14 days of sodium restriction. Extracellular fluid volume and cardiac output decreased. Blood pressure was unchanged but there was an increase in peripheral resistance and plasma renin concentration.