Effect of forward acceleration on renal function

¹ Aerospace Medical Laboratory, Aeronautical Systems Division, Wright-Patterson Air Force Base, Ohio

The effect of forward acceleration on renal hemodynamics, electrolyte excretion, and water clearance has been studied in six normal human subjects. Forward acceleration produced a slight increase in glomerular filtration rate and effective renal plasma flow during and after stress. After centrifugation there was a 20–35-min lag before the appearance of an increase in urine volume and free water clearance. These changes in water excretion were transient and were not accompanied by a natriuresis nor associated with changes in serum osmolality. Physiologic responses to forward acceleration and negative pressure breathing were compared. It was suggested that forward acceleration, like negative pressure breathing, may induce an increase in intrathoracic blood volume which inhibits the release of antidiuretic hormone via a nonosmotic volume-sensitive receptor mechanism located within the intrathoracic vascular space.