Transient physiological changes in DOCA-Dahl rats in hydrocephalus

Abstract

AV3V lesions prevent DOCA-NaCl hypertension (HTN). To check effects of NaCl diets and hydrocephalic brains in post-DOCA HTN, baseline, transient physiological changes and long term adjusted results were examined. DOCA HTN was induced in 36 Dahl R rats with 250 mg/kg DOCA in silicone and saline water containing 1% NaCl and 0.2% KCl. After 4 weeks, the DOCA and saline were removed and the rats were on a recovery period with tap water and a 0.3% low NaCl chow. One week later, the aqueduct of Sylvius was blocked in one group and the other group had a sham block. The blood pressure (BP) matched 2 groups (154 mm Hg) were kept on the low NaCl diet for another 4 weeks to produce hydrocephalus. Then both groups had an 8% high NaCl chow. A transient change in plasma Na level was observed in the truly blocked group after 48 hours of the 8% high NaCl diet, 134.9 ± 2.4 mEq/L, while the sham group averaged 141.1±1.9 mEq/L, p<0.05. We also observed markedly increased water and Na intake, and tissue water accumulation in the sham group (all p<0.0001). After adjustment of the surgery and diet interaction, the values were still significantly increased in the sham group, p<0.0001. After 4 weeks on the diet, the plasma Na levels of the two groups were similar to each other (141 vs. 140 mEq/L), although the sham group BPs were significantly higher than that of the blocked group, 171 vs. 147 mm Hg (p<0.0001). In our previous reports, the aqueduct block showed markedly reduced BPs, mortality rates, cardiac hypertrophy and urinary albumin. We do not know what the mechanism is involved in the transient changes, however, the protective effect in BPs may be due to the readjustment of the fluid or electrolyte imbalance in the volume expansion of the hydrocephalic brain.