AJP - Renal Physiology, Vol 233, Issue 5 428-F437, Copyright © 1977 by American Physiological Society
Renal concentrating ability in the uninephrectomized rat
E. Sachtjen, L. Rabinowitz and P. E. Binkerd
To investigate the effects of uninephrectomy on renal concentrating
ability, studies were performed on unanesthetized rats 5-11 days after
uninephrectomy (UN) or a sham operation (SO). Female rats were deprived of
water for 27 h prior to the infusion of inulin and para-aminohippurate and
urine collection. They were also preconditioned to being handled and to the
experimental locale. During a nondiuretic state urine osmolality was the
same for all UN and SO groups (mean about 1,700 micro osmol/g H2O), whereas
the mean solute excretion rate (micro osmol/min per kg body wt per kidney)
was 74 in the UN and 35 in the SO rats. When SO rats were infused with
mannitol or isotonic saline to increase their solute excretion rate per
kidney to the level of the UN rats, urine osmolality dropped 200-1,000
micro osmol/g H2O; when urea was infused, urine osmolality did not drop.
Thus, after uninephrectomy and a consequent doubling of the solute
excretion rate per kidney, renal concentrating ability was higher than
predicted on the basis of a comparable but acute elevation of the solute
excretion rate. The glomerular filtration rate was about 17 ml/min per kg
body wt in the SO rats and was 1.2 times greater (on a per kidney basis) in
the UN rats. These exceptionally high glomerular filtration rats are
attributed to preexperimental conditioning of the rats and the absence of
stress during urine collection.
