Sodium intake and exchangeable sodium in hypertensive rats.

Exchangeable sodium, extracellular fluid volume and sodium intake were significantly higher in spontaneously hypertensive rats (SHR) than in normotensive controls. The increased exchangeable sodium was due to the expanded extracellular fluid sodium content. Two kidney one clip Goldblatt renal hypertensive rats develop thirst and high renin levels. When drinking saline the rats have markedly increased exchangeable sodium levels, but those drinking water did not. It is proposed that the exaggerated saline intake leads to a volume dependent component of the hypertension in both models. In the SHR both the salt appetite and the hypertension may be induced by angiotensin acting via central mechanisms.