CHRONIC MANIPULATION OF DIETARY SALT MODULATES RENAL PHYSIOLOGY AND KIDNEY DOPAMINE-RECEPTOR SUBTYPES - FUNCTIONAL AND AUTORADIOGRAPHIC STUDIES

1. Compared to rats maintained on the normal NaCl (0.33%) diet, animal s maintained on the low NaCl (0%) diet for 4 weeks exhibited increased plasma aldosterone and chloride and decreased urinary sodium excretio n. 2. Rats maintained on the high NaCl (8%) diet for 4 weeks showed in creased systolic blood pressure, water intake, urine volume, sodium an d dopamine excretion and decreased plasma aldosterone and glomerular f iltration rate. 3. Administration of SCH 23390 (10 mg/kg, po), but not domperidone to the high salt diet rats attenuated the diuretic effect , indicating the involvement of DA(1) rather than DA(2) receptors. The dopamine decarboxylase inhibitor, carbidopa (30 mg/kg, i.p.), also re duced the high salt-induced diuresis. 4. Kidney sections from rats fed the low NaCl diet showed a 63-100% decrease (P < 0.001-0.02) in corti cal and medullary DA(1) and DA(2) binding sites, while rats fed the hi gh NaCl diet demonstrated only a 70% decrease (P < 0.01-0.02) in corti cal DA(1) binding, without affecting DA(2) binding. 5. These data indi cate that chronic modification of dietary salt profoundly affects the sodium, water and dopamine excretion and leads to selective modulation of renal dopamine receptor subtypes.