Lv. Rossoni et al., Effects of small doses of ouabain on the arterial blood pressure of anesthetized hypertensive and normotensive rats, BRAZ J MED, 34(8), 2001, pp. 1065-1077
Citations number
40
Categorie Soggetti
Medical Research General Topics
Journal title
BRAZILIAN JOURNAL OF MEDICAL AND BIOLOGICAL RESEARCH
Ouabain increases vascular resistance and may induce hypertension by inhibi
ting the Na+ pump. The effects of 0.18 and IS mug/kg, and 1.8 mg/ kg ouabai
n pretreatment on the phenylephrine (PHE; 0.1, 0.25 and 0.5 pg, in bolus)-e
voked pressor responses were investigated using anesthetized normotensive (
control and uninephrectomized) and hypertensive (1K1C and DOCA-salt treated
) rats. Treatment with 18 mug/kg ouabain increased systolic and diastolic b
lood pressure in all groups studied. However, the magnitude of this increas
e was larger for the hypertensive 1K1C and DOCA-salt rats than for normoten
sive animals, while the pressor effect of 0. 18 mug/kg ouabain was greater
only in DOCA-salt rats. A very large dose (1.8 mg/kg) produced toxic effect
s on the normotensive control but not on uninephrectomized. or 1K1C rats. R
at tail vascular beds were perfused to analyze the effects of 10 nM ouabain
on the pressor response to PHE. In all animals, 10 nM ouabain increased th
e PHE pressor response, but this increase was larger in hypertensive DOCA-s
alt rats than in normotensive and 1K1C rats. Results suggested that a) incr
eases in diastolic blood pressure induced by 18 mug/kg ouabain were larger
in hypertensive than normotensive rats; b) in DOCA-salt rats, smaller ouaba
in doses had a stronger effect than in other groups; c) hypertensive and un
inephrectomized rats were less sensitive to toxic doses of ouabain, and d)
after treatment with 10 nM ouabain isolated tail vascular beds from DOCA-sa
lt rats were more sensitive to the pressor effect of PRE than those from no
rmotensive and 1K1C hypertensive rats. These data suggest that very small d
oses of ouabain, which might produce nanomolar plasma concentrations, enhan
ce pressor reactivity in DOCA-salt hypertensive rats, supporting the idea t
hat endogenous ouabain may contribute to the increase and maintenance of va
scular tone in hypertension.