Thirst and sodium appetite in rats with experimental nephrotic syndrome.

Nephrotic syndrome is a renal disease accompanied by abnormal body fluid balance. The present experiments investigated the role of behavioral mechanisms in contributing to disordered fluid homeostasis in rats with experimentally-induced nephrotic syndrome. The studies examined water and sodium ingestion under ad libitum conditions and in response to dehydration-related challenges in rats made nephrotic by treatment with the antibiotic, adriamycin. Rats with nephrotic syndrome had greater ad libitum water intakes beginning 3 weeks after treatment, but daily sodium (0.3M NaCl) intakes were not affected. Nephrotic rats showed attenuated water and sodium intakes after combined treatment with furosemide (10mg/kg) and captopril (2mg/kg), reduced water intakes after 20h of water deprivation, and diminished water intakes, plasma renin activity and aldosterone secretion after subcutaneous isoproterenol (30 μg/kg). However, the adriamycin-treated animals had normal water intakes in response to subcutaneous hypertonic saline (4% at 0.75 ml/100g) and central injections of angiotensin II (10, 20, and 50 ng). The results suggest that water and sodium ingestion in response to hypovolemic/hypotensive stimuli are disturbed in nephrotic rats, and provide evidence that the disordered behaviors reflect disturbances of the peripheral renin-angiotensin-aldosterone system.