AJP - Heart and Circulatory Physiology, Vol 247, Issue 6 902-H908, Copyright © 1984 by American Physiological Society
Na transport and blood pressure in the adrenalectomized rat
S. M. Friedman, R. A. McIndoe and M. Tanaka
The transmembrane distribution of Na, K, and water in freshly excised rat
tail artery was measured 7 days after adrenalectomy, 3 days after
withdrawal of support with 1% NaCl as drinking water. Cell Na decreased
from 35.8 +/- 0.9 to 31.6 +/- 0.7 mmol/kg dry wt, tissue water increased
from 2.93 +/- 0.03 to 3.08 +/- 0.04 l/kg dry wt, and tissue K remained
unchanged. As concentration, [Na]i decreased from 22.5 +/- 0.9 to 18.3 +/-
1.0 mM in parallel with [Na]o which fell from 140.6 +/- 0.3 to 133.6 +/-
1.0. Conversely, while [K]i fell from 140 +/- 2 to 128 +/- 3, [K]o rose
from 2.15 +/- 0.12 to 5.40 +/- 0.33 so that EK dropped from -109 to -83 mV.
Aldosterone (120 micrograms X 100 g-1 X 24 h-1 sc; 3 X 10(-7) M if
immediately distributed in the extracellular fluid) partially restored
blood pressure, plasma [Na] and [K], and tissue water within 24-26 h but
did not increase cell Na. Similar effects were produced with corticosterone
at 400 microgram X 100 g-1 X 24 h-1 (3 X 10(-6) M if immediately
distributed in the extracellular fluid). We conclude that the restoration
of blood pressure in the adrenalectomized rat is independent of [Na]i or
[Na]o/[Na]i but is associated with enhanced Na transport activity.
