Abstract
To investigate age-associated impairments in fluid homeostasis, 4-mo (young) and 32-mo (old) Fischer 344/BN male rats were studied before and after a dietary sodium load. Transferring young rats from a low-sodium (LS) to a high-sodium (HS) diet increased water intake and urine volume by 1.9-and 3.0-fold, respectively, while urine osmolality and plasma aldosterone decreased by 33 and 98%. Concomitantly, adrenocortical angiotensin type 1 receptor (AT1R) density decreased by 35%, and AT1bR mRNA decreased by 39%; no changes were observed in AT1aR mRNA. In contrast, the increase in water intake (1.4-fold) was lower in the old rats, and there was no effect of the HS diet on urine volume or urine osmolality. AT1R densities were 29% less in the old rats before transferring to the HS diet, and AT1R densities were not reduced as rapidly in response to a HS diet compared with the young animals. After 6 days on the HS diet, plasma potassium was lowered by 26% in the old rats, whereas no change was detected in the young rats. Furthermore, while plasma aldosterone was substantially decreased after 2 days on the HS diet in both young and old rats, plasma aldosterone was significantly lower in the old compared with the young animals after 2 wk on the LS diet. These findings suggest that aging attenuates the responsiveness of the adrenocortical AT1R to a sodium load through impaired regulation of AT1bR mRNA, and that this dysregulation contributes to the defects in water and electrolyte homeostasis observed in aging.
Recommended Citation
H. Ji et al., "Aging-related Impairment of Urine-concentrating Mechanisms Correlates with Dysregulation of Adrenocortical Angiotensin Type 1 Receptors in Male Fischer Rats," American Journal of Physiology Regulatory Integrative and Comparative Physiology, vol. 310, no. 6, pp. R513 - R521, American Physiological Society, Mar 2016.
The definitive version is available at https://doi.org/10.1152/ajpregu.00131.2015
Department(s)
Biological Sciences
Publication Status
Open Access
Keywords and Phrases
Adrenal cortex; Aldosterone; Angiotensin type 1 receptor and angiotensin type 2 receptor messenger ribonucleic acid; Urine osmolality; Urine volume
International Standard Serial Number (ISSN)
1522-1490; 0363-6119
Document Type
Article - Journal
Document Version
Final Version
File Type
text
Language(s)
English
Rights
© 2025 American Physiological Society, All rights reserved.
Creative Commons Licensing
This work is licensed under a Creative Commons Attribution 4.0 License.
Publication Date
01 Mar 2016
PubMed ID
26702152
Comments
National Institutes of Health, Grant R01-AG-19291