The effect of hypertension and its treatment on cerebral cell volume regulation during hypernatremic dehydration

Since hypertension may compromise the ability to withstand hypernatremic dehydration, we investigated the impact of two experimental models of hypertension and pharmacologic normalization of blood pressure on the tolerance to chronic hypernatremic dehydration. In DOCA-salt hypertensive animals and the spontaneously-hypertensive rat (SHR), there was increased mortality and cerebral cell shrinkage during hypernatremic dehydration, compared to control Sprague-Dawley or Wistar-Kyoto rats. These findings were paralleled by significant differences in the brain intracellular water compartment size (ml/100 g dry weight), i.e. 233 +/- 6, Sprague-Dawley vs 189 +/- 8, DOCA-salt, P less than 0.01; 246 +/- 3, Wistar-Kyoto vs 194 +/- 6, SHR, P less than 0.01. Normalization of the blood pressure in the SHR with captopril restored 48% of the cerebral cell volume regulatory capacity observed in normotensive Wistar-Kyoto rats. We conclude that sustained hypertension increases the risk of hypernatremic dehydration in select circumstances. Correction of the elevated blood pressure promotes partial recovery of normal cerebral cell volume regulation.