Age-related changes in thirst, salt appetite, and arterial blood pressure in response to aldosterone-dexamethasone combination in rats

Abstract

This work examined the effects of age on daily water and sodium ingestion and cardiovascular responses to chronic administration of the mineralocorticoid, aldosterone (ALDO) either alone or together with the glucocorticoid, dexamethasone (DEX). Young (4 mo), adult (12 mo), and aged (30 mo) male Brown Norway rats were prepared for continuous telemetry recording of blood pressure (BP) and heart rate (HR). Baseline water and sodium (i.e., 0.3 M NaCl) intake, BP, and HR were established for 10 days. Then ALDO (60 μg/day sc) was infused alone, or together with DEX (2.5 or 20 μg/day sc), for another 10 days. Compared with baseline levels, ALDO stimulated comparable increases in daily saline intake at all ages. ALDO together with the higher dose of DEX (i.e., ALDO/DEX20) increased daily saline intake more than did ALDO, but less so in aged rats. Infusion of ALDO/DEX20 increased mean arterial pressure (MAP), and decreased HR, more than did infusion of ALDO. The changes in MAP in response to both treatments depended on age. For all ages, MAP and saline intake increased simultaneously during ALDO, while MAP always increased before saline intake did during ALDO/DEX20. Contrary to our predictions, MAP did not increase more in old rats in response to either treatment. We speculate that age-related declines in cardiovascular responses to glucocorticoids contributed to the attenuated increases in sodium intake in response to glucocorticoids that were observed in older animals.

Increased activity of the orexin system in the paraventricular nucleus contributes to salt-sensitive hypertension

“…Before diet treatment, 7-wk-old male SD and Dahl S rats were anesthetized, and telemetry transmitters (HD-S11, Data Science, St. Paul, MN) were implanted to directly measure arterial blood pressure in individual animals. Briefly, rats were anesthetized with isoflurane (2-3%), a catheter connected to a telemetry transmitter was inserted into the femoral artery, and the transmitter was placed subcutaneously (51). After 1 wk of recovery from the surgery, animals were randomly divided into two groups and were fed either the NS or HS diet.…”

Porphyran from Porphyra haitanensis Enhances Intestinal Barrier Function and Regulates Gut Microbiota Composition

“…The genus of Lachnospira , Lachnoclostridium , Fusicantenibacter , Roseburia , Eubacterium , Ruminococcus , and some genera from Bacteroidetes are the major butyrate producer for gut mucosal immune regulation and functional marker of healthy mature anaerobic gut microbiota [ 50 ]. Coprococcus plays a significant role in the production of vitamin B and SCFAs [ 51 , 52 ]. The Faecalibacterium prausnitzii , Roseburia intestinalis , and Agathobacter rentals are the common bacteria known to produce butyrate [ 53 ].…”