Effect of lifelong high- or low-salt intake on blood pressure, left ventricular mass and plasma insulin in Wistar rats.
BACKGROUND
Salt restriction is recommended for hypertension treatment to reduce blood pressure, but its effect on some risk factors is still a matter of discussion. The aim of this study was to observe the effect of a long period of salt restriction or overload on blood pressure, left ventricular mass (LVM), kidney mass (KM), glucose tolerance, and plasma insulin.


METHODS
Male Wistar rats were fed from weaning with a low-salt diet (LSD) or a high-salt diet (HSD) until 72 weeks of age. After 48 weeks, the diets were changed in half of the rats: HSD until 48 weeks and then LSD (LHSD) and LSD until 48 weeks and then HSD (HLSD). Body weight, blood pressure, electrolyte excretion, creatinine clearance, plasma renin activity, LVM, KM, and intravenous glucose tolerance test with insulin determinations were evaluated.


RESULTS
Blood pressure, LVM and KM were higher on the HSD than on the LSD. Blood pressure was lower on the LHSD than on the HLSD. There were no differences in LVM and KM on the LHSD compared with the HLSD. The relationship between area under the curve (AUC) of insulin and glucose during the intravenous glucose tolerance test was higher on the LSD. No differences were detected in AUC between the two groups of rats whose diet were inverted with 48 weeks of age.


CONCLUSIONS
A chronic HSD increases blood pressure, LVM, and KM and a chronic LSD increases plasma insulin in response to a glucose challenge in aging rats. The hypotensive effect of salt restriction is not modified by a previous long period on a HSD.
Lima
Nereida K C
NK
Division of General Internal and Geriatric Medicine, Department of Internal Medicine, Ribeirão Preto Medical School, São Paulo, Brazil.
Lima
Fabio B
FB
dos Santos
Elisabete A
EA
Okamoto
Maristela M
MM
Sumida
Doris H
DH
Hell
Naomi S
NS
Furukawa
Luzia N S
LN
Heimann
Joel C
JC
D000375:Aging / Q000378:metabolism / Q000473:pathology; D000818:Animals; D019540:Area Under Curve; D001794:Blood Pressure / Q000187:drug effects*; D001835:Body Weight; D004039:Diet, Sodium-Restricted; D005951:Glucose Tolerance Test; D006321:Heart / Q000187:drug effects*; D006352:Heart Ventricles / Q000187:drug effects; D007328:Insulin / Q000097:blood*; D007333:Insulin Resistance; D007668:Kidney / Q000187:drug effects; D008297:Male; D009206:Myocardium / Q000473:pathology; D051381:Rats; D017208:Rats, Wistar; D012083:Renin / Q000097:blood; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage* / Q000494:pharmacology*
D007328:Insulin; D017673:Sodium Chloride, Dietary; D012083:Renin