THIRST AND FLUID REGULATORY RESPONSES TO HYPERTONICITY IN OLDER ADULTS

Citation
Ns. Stachenfeld et al., THIRST AND FLUID REGULATORY RESPONSES TO HYPERTONICITY IN OLDER ADULTS, American journal of physiology. Regulatory, integrative and comparative physiology, 40(3), 1996, pp. 757-765
Citations number
26
Categorie Soggetti
Physiology
ISSN journal
03636119
Volume
40
Issue
3
Year of publication
1996
Pages
757 - 765
Database
ISI
SICI code
0363-6119(1996)40:3<757:TAFRRT>2.0.ZU;2-C
Abstract
To assess the fluid regulatory responses in aging adults, we measured thirst perception and renal osmoregulation during and after infusion o f hypertonic (3% NaCl) saline in older (72 +/- 2 yr, n = 6) and younge r (26 +/- 2 yr, n = 6) subjects. Hypertonic saline was infused at 0.1 ml . min(-1). kg(-1) for 120 min. On a separate day, the same subjects were infused identically with isotonic saline as a control. After inf usion and a 30-min equilibration period, the subjects drank water ad l ibitum for 180 min. Hypertonic saline infusion Zed to graded increases in plasma osmolality (P-osm; 18 +/- 2 and 20 +/- 2 mosmol/kgH(2)O) an d percent changes in plasma volume (16.2 +/- 1.9 and 18.0 +/- 1.2%) th at were similar in older and younger subjects. Osmotically stimulated increases in thirst (94.8 +/- 18.9 and 88.3 +/- 25.6 mm), assessed on a line rating scale, and plasma arginine vasopressin concentration (6. 08 +/- 1.50 and 4.51 +/- 1.37 pg/ml, for older and younger, respective ly) were also unaffected by age. Despite subsequent hypervolemia, both groups of subjects drank sufficient water to restore preinfusion leve ls of P-osm. Renal handling of free water and sodium was also unaffect ed by age during recovery from hypertonic saline infusion, but was sig nificantly lower in older subjects during recovery from isotonic salin e infusion, resulting in net fluid retention and a significant fall in P-osm (6 mosmol/kgH(2)O). In contrast to earlier reports of a blunted thirst response to dehydration and hypertonicity, we found that osmot ically stimulated thirst and renal osmoregulation were intact in older adults after hypertonic saline infusion.