Hearing loss. vertigo, and tinnitus have been related to arterial hypertens
ion. The aim of the present work was to study the permeability of the blood
-perilymph and of the labyrinthine barrier, between endolymph and perilymph
, to small molecules during chronic and acute hypertension. Experiments wer
e performed in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensi
ve rats (SHR). Acute hypertension was induced by phenylephrine. Perilymph w
as sampled from the first turn of the scala vestibuli and the Na, K, urea,
and radioactive concentrations (C-14-urea and H-3-mannitol) were measured.
In another experimental set, the endocochlear potential was recorded from t
he basal turn of scala media, before and after phenylephrine injection. The
composition of the perilymph and the kinetic constants for C-14-urea and 3
H-mannitol were similar in WKY and SHR, and not modified after acute hypert
ension. In endolymph, the endocochlear potential in SHR (+80 +/- 2.7 mV, n
= 24) was lower (P < 0.001) than in WKY (+98 +/- 1.5 mV, n = 29). The endoc
ochlear potential was decreased by 40 mV during acute hypertensive peak in
seven out of 19 WKY but not in SHR rats (n = 13). In conclusion, chronic or
acute hypertension did not severely alter the permeability to small molecu
les of the blood-perilymph barrier. The relationship between the low endoco
chlear potential and hypertension in SHR remains to be evaluated. After acu
te hypertensive peak, the presence of vascular protective mechanisms in the
cochlea could account for the stable endocochlear potential recorded in SH
R and 60% of normotensive rats. (C) 2001 Elsevier Science B.V. All rights r
eserved.