The Blood Brain Barrier in Renal Hypertensive Rats

Abstract

Spontaneously hypertensive rats (SHR) are less prone to develop a dysfunction of the blood-brain barrier (BBB) when exposed to an abrupt increase in blood pressure than normotensive rats (NR), probably as a result of vessel wall hypertrophy and increased vessel wall to lumen ratio. Hemodynamic studies have indicated that structural adaptation develops early as a response to the increased pressure load in renal hypertensive rats (RHR). In the present study RHR (one renal artery constricted and the contralateral kidney intact) were subjected to acute hypertension induced by bicuculline, a drug that induces an abrupt increase in blood pressure concomitant with pronounced cerebral vasodilatation. Protein leakage in the brain, as indicated by Evans blue-albumin and ¹²⁵IHSA (human serum albumin) extravasation, was not reduced in RHR compared to NR. The cerebrovascular permeability was slightly but significantly (p<0.01) increased in RHR even in the absence of further blood pressure manipulation. No neurological symptoms were observed in conscious RHR when the BBB dysfunction was aggravated by hypercapnia. The increased cerebrovascular permeability in RHR could be due to a lower degree of structural adaptation in RHR compared to SHR and/or to some permeability-increasing humoral factor in renal hypertension.