AJP - Renal Physiology, Vol 249, Issue 5 753-F758, Copyright © 1985 by American Physiological Society
Fasting induces denervation natriuresis in the conscious rat
G. Szenasi, P. Bencsath, L. Szalay and L. Takacs
The participation of renal nerves in the regulation of sodium excretion was
studied in fed and overnight-fasted rats subjected to acute or chronic left
kidney denervation or sham operation. Clearance experiments were performed
on conscious restrained animals. Urine flow, glomerular filtration rate
(GFR), and urinary sodium excretion were not different in left and right
kidneys of sham-operated rats. In fed conscious rats, urine flow, GFR, and
urinary sodium excretion of innervated (I) and denervated (D) kidneys were
similar. In fasted conscious rats, significant denervation natriuresis was
observed after both acute (I, 1.06 +/- 0.27; D, 1.56 +/- 0.40 mumol . min-1
. g-1, P less than 0.05) and chronic (I, 1.55 +/- 0.19; D, 2.20 +/- 0.18
mumol . min-1 . g-1, P less than 0.01) renal sympathectomy, whereas urine
flow and GFR in I and D kidneys were not different. Additional experiments
revealed that extracellular fluid and plasma volumes of fasted rats were
decreased by approximately 10% compared with those of fed animals due to a
significant overnight natriuresis and negative water balance. In fed
conscious rats, the renal nerves do not seem to participate in the
regulation of sodium excretion. The presence of denervation natriuresis in
conscious fasted rats suggests that renal nerves are involved in sodium
conservation during fasting to maintain extracellular fluid and plasma
volume.
