The effect of vagotomy on sodium reabsorption and renin release in anaesthetized dogs subjected to 60 degrees head-up tilt.

Abstract

1. Anaesthetized dogs were subjected to two 15 min periods of 60 degrees head-up tilt. Renal perfusion pressure was regulated to minimize changes during tilting. 2. In both intact and vagotomized animals there was a fall in systemic arterial pressure and a rise in heart rate. In both intact and vagotomized animals glomerular filtration rate fell slightly during the first tilt but remained unchanged in the second tilt period. Renal blood flow was unchanged throughout. 3. Both absolute and fractional excretions of sodium were reduced in intact animals subjected to the two consecutive periods of tilt. Following vagotomy these responses were as large as those observed in intact animals. 4. Tilting caused an increase in renin secretion from the kidney in both tilting periods to which the intact animals were subjected. In the vagotomized animals the increase in renin secretion was as large as that observed in intact animals. 5. The results of the present study show that, under the experimental conditions used, vagal afferent activity had no measurable effect on the decreases in sodium excretion or increases in renin secretion mediated by the renal nerves during short periods of 60 degrees head-up tilt.