AJP - Renal Physiology, Vol 257, Issue 3 341-F346, Copyright © 1989 by American Physiological Society
Volume receptors in guinea pig labyrinth: relevance with respect to ADH and Na control
E. Bartoli, A. Satta, F. Melis, M. A. Caria, W. Masala, G. Vargiu, F. Meloni, G. P. Teatini and G. B. Azzena
Institute of Physiology, University of Sassari Medical School, Italy.
We tested the hypothesis that changes in extracellular fluid volume are
reflected by pressure changes within structures of the inner ear and that
through neural pathways, a control mechanism exerts an influence on
antidiuretic hormone (ADH) release and Na excretion. The study was
performed on 35 guinea pigs. In protocol 1, 13 animals were studied before
and after decompression of the inner ear by bilateral fluid withdrawal in
an experimental setting of sustained isotonic expansion that kept the
osmoreceptor partially activated and the intrathoracic volume receptors
suppressed. A group of six sham-operated animals served as control. In
protocol 2, nine animals were studied before and after a unilateral rise in
their inner ear pressure during slightly hypertonic low-rate infusions that
kept the osmoreceptor and thoracic volume receptors stimulated. A group of
seven sham-operated guinea pigs served as controls. Decompression of the
inner ear was attended by a rise in plasma ADH from 11.9 +/- 2.4 to 29.1
+/- 6.9 pg/ml, in urine osmolality (Uosmol) from 470 +/- 48 to 712 +/- 46
mosmol/kg (P less than 0.001), and a fall in urine flow rate (V) from 184
+/- 47 to 71 +/- 11 microliters/min (P less than 0.01), whereas plasma Na
(PNa) and osmolality (Posmol) did not change. During inner ear
hypertension, plasma ADH fell from 25.6 +/- 3.9 to 18.4 +/- 3.1, Uosmol
from 829 +/- 58 to 627 +/- 43 (P less than 0.001), and V rose from 51 +/-
11 to 130 +/- 23 (P less than 0.001), whereas glomerular filtration rate,
PNa, and Posmol did not change.(ABSTRACT TRUNCATED AT 250 WORDS)
