Journal of Applied Physiology, Vol 71, Issue 2 716-720, Copyright © 1991 by American Physiological Society
Passive heat exposure leads to delayed increase in plasma levels of atrial natriuretic peptide in humans
J. Leppaluoto, O. Arjamaa, O. Vuolteenaho and H. Ruskoaho
Department of Physiology, University of Oulu, Finland.
The effects of passive heat exposure on atrial natriuretic peptide (ANP)
were studied in six healthy men staying in a Finnish sauna at +92 degrees C
for 20 min. Their rectal temperature increased by 0.4 degrees C, and
evaporative water loss was 0.92 +/- 0.14 (SD) kg. Heart rate and systolic
blood pressure increased significantly during the 20-min exposure. Serum
osmolality and plasma arginine vasopressin levels increased during the
exposure, then declined, and increased significantly again at 90-120 min.
Plasma renin activity and aldosterone increased by two- to fourfold in 20
min. Plasma ANP levels rose from 13 +/- 7 to 39 +/- 15 ng/l at 60 min and
to 41 +/- 13 ng/l at 120 min (P less than 0.01 for both). We conclude that
transient increases in heart rate and systolic blood pressure or changes in
blood volume as inferred from the weight loss do not contribute to the
increased plasma ANP levels observed after the heat exposure. Instead,
increased secretions of pressor hormones could explain the elevated plasma
ANP levels observed after the thermal stress.
