The Effect of Different Water Temperatures on the Release of the Atrial Natriuretic Factor (ANF) During 'Head Out Water Immersion (HOI)"

Head-out water immersion (HOI) results in a redistribution of blood volume with a relative central hypervolemia, which is the cause of increased secretion of the atrionatriuretic factor (ANF). This study was conducted to examine the role of different bath temperatures for the stimulation of ANF secretion. Twelve healthy subjects were immersed in 4 water baths (24, 28. 35 and 39 *C) for 40 min in a randomized fashion. Plasma ANF was determined by radioimmunoassay following extraction. The baths led to a significant increase in plasma ANF. Maximal increments were the highest in hot baths. This data suggests that heat induced changes in circulation may modulate the secretion of ANF. The importance of heart rate is being discussed.