Effects of high salt intake on brain AT1 receptor densities in Dahl rats.
To assess effects of dietary salt on brain AT1 receptor densities, 4-wk-old Dahl salt-sensitive (Dahl S) and salt-resistant (Dahl R) rats were fed a regular (101 mumol Na/g) or high (1,370 mumol Na/g)-salt diet for 1, 2, or 4 wk. AT1 receptors were assessed by quantitative in vitro autoradiography. AT1 receptor densities did not differ significantly between strains on the regular salt diet. The high-salt diet for 1 or 2 wk increased AT1 receptor binding by 21-64% in the Dahl S rats in the subfornical organ, median preoptic nucleus, paraventricular nucleus, and suprachiasmatic nucleus. No changes were noted in the Dahl R rats. After 4 wk on a high-salt diet, increases in AT1 receptor binding persisted in Dahl S rats but were now also noted in the paraventricular nucleus, median preoptic nucleus, and suprachiasmatic nucleus of Dahl R rats. At 4 wk on the diet, intracerebroventricular captopril caused clear decreases in blood pressure only in the Dahl S on the high-salt diet but caused largely similar relative increases in brain AT1 receptor densities in Dahl S and R on the high-salt diet versus regular salt diet. These data demonstrate that high salt intake rapidly (within 1 wk) increases AT1 receptor densities in specific brain nuclei in Dahl S and later (by 4 wk) also in Dahl R rats. Because the brain renin-angiotensin system only contributes to salt-induced hypertension in Dahl S rats, further studies are needed to determine which of the salt-induced increases in brain AT1 receptor densities contribute to the hypertension and which to other aspects of body homeostasis.
Wang
Jun Ming
JM
Hypertension Unit, University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, Ontario, Canada K1Y 4W7.
Veerasingham
Shereeni J
SJ
Tan
Junhui
J
Leenen
Frans H H
FH
D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D001923:Brain Chemistry / Q000187:drug effects* / Q000502:physiology; D002216:Captopril / Q000494:pharmacology; D006706:Homeostasis / Q000187:drug effects; D006973:Hypertension / Q000139:chemically induced / Q000378:metabolism*; D007276:Injections, Intraventricular; D007672:Kidney Cortex / Q000378:metabolism; D007679:Kidney Medulla / Q000378:metabolism; D008297:Male; D051381:Rats; D020303:Rats, Inbred Dahl; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism*; D017673:Sodium Chloride, Dietary / Q000494:pharmacology*
D000959:Antihypertensive Agents; D044140:Receptor, Angiotensin, Type 1; D017673:Sodium Chloride, Dietary; D002216:Captopril