Abstract
Angiotensin II (ANG II) is involved in the renal sodium homeostasis in
close relation with sympathetic nervous system (SNS) under normal and
pathological conditions. Vasopressin (AVP), a hormone that modulates
renal sodium and water reabsorptionis synthetized and released from
supraoptic (SON) and paraventricular nucleus (PVN) under ANG II
influence. We hypothesized that brain ANG II AT1 receptors (AT1-R)
regulate renal sodium and water reabsorption and excretion through SNS.
In this study male Wistar rats with renal denervation/sham and fed with
hypersodic (4%) or normal (0.4%) diet were evaluated during 5 days in
metabolic cages. On day 5 were injected in lateral ventricle with
losartan (AT1-R antagonist) and sacrificed 12 hours later. The urine was
daily collected, blood samples and brains were obtained for
determinations. The parameters analyzed were: a) c-Fos immunoreactivity
in SON, PVN, subfornical (SFO) and organum vasculosum of the lamina
terminalis nucleus (OVLT), b) c-Fos-AVP immunoreactivity in SON in sham
group, c) sodium and water intake, d) water, sodium and creatinine
excretion. Results: c-Fos expression in SFO, OVLT and PVN was
differentially affected by hypersodic diet or losartan depending on
renal nerve integrity. In sham animals losartan prevented the hypersodic
diet effects in water intake, c-Fos and AVP positive neurons in SON.
Renal denervation modified the effect of hypersodic diet in water
intake, urinary volume and creatinine excretion; losartan prevented
these alterations. Food intake was similar in all groups. Our results
suggest that brain AT1-R regulate renal sodium and water reabsorption
through SNS in close interaction with AVP.