Journal of Applied Physiology, Vol 73, Issue 5 1785-1790, Copyright © 1992 by American Physiological Society
Modification of water and electrolyte metabolism during head-down tilting by hypoglycemia in men
Y. Hayashi, Y. Murata, H. Seo, N. Miyamoto, F. Kambe, S. Ohmori, C. Yamamoto, S. Hayamizu, Y. Tamura and N. Matsui
Department of Endocrinology and Metabolism, Nagoya University, Japan.
The effect of hypoglycemic stress on the changes in water and electrolyte
metabolism induced by head-down tilting (HDT) was studied. Six healthy men
were subjected to postural changes (30 min standing, 2 h HDT, 1 h
standing), with or without the intravenous administration of insulin at the
beginning of HDT. When insulin was not given, antidiuretic hormone (ADH),
cortisol, plasma renin activity (PRA), aldosterone, and catecholamine
levels were decreased and atrial natriuretic polypeptide (ANP) levels
increased during HDT. These changes were associated with 2.5- and 1.5-fold
increases in urine flow and sodium excretion, respectively, when compared
with the amounts before HDT. On the other hand, insulin-induced
hypoglycemia during HDT produced increases in ADH, cortisol, PRA,
aldosterone, and catecholamine levels. At the same time, an exaggerated ANP
response by HDT was observed. These hormonal changes were associated with
an abolishment of the increases in urine flow and sodium excretion. It is
suggested that acute stress modifies the changes in fluid and electrolyte
metabolism induced by HDT.
