The excretion of sodium, potassium and water, and the changes of glomerular filtration rate (g.f.r.) in response to intravenous infusions of hypertonic saline have been studied in normal and adrenalectomized rats.
The increase in sodium excretion in response to infusion was considerably depressed after adrenalectomy. It was not restored to normal by cortisone or cortisol administration, although the adrenalectomized rats treated with these steroids were able to excrete water after a water load as rapidly as normal rats.
Potassium excretion was increased to a similar extent by the infusions in both normal and adrenalectomized rats.
g.f.r. rose in both groups during the infusion but the rise was depressed by adrenalectomy. In both normal and adrenalectomized rats treated with cortisone, g.f.r. remained elevated throughout the infusion, but the initial rise was less rapid in the latter than in the normal animals. In adrenalectomized rats maintained on 1% saline only, the rise of g.f.r. was not sustained and by the 4th hr of infusion had fallen to the pre-infusion level. When i.v. cortisol was given immediately before the infusion, the initial rise of g.f.r. was restored to normal.
Comparison of the changes of g.f.r. with those of sodium excretion suggested that impairment of sodium excretion during the infusions was due, in part at least, to a change in renal tubular reabsorption of sodium following adrenalectomy.