title: Effect of increased dietary phosphate intake on dopamine excretion in the presence and absence of the renal nerves.
abstract: Studies were performed to determine the relative contributions of the renal nerves and tubule synthesis to dopamine excretion during increased dietary phosphate intake. Rats underwent bilateral renal denervation (n = 5) or sham surgery (n = 5) 1 week prior to the initiation of the balance studies. All rats were placed in metabolic cages and fed 12 g/day of a low phosphate diet (LPD, 0.07%, Pi) for 4 days, then high phosphate diet (HPD, 1.8% Pi) for 4 days. Sodium, potassium, and chloride contents were made similar in LPD and HPD by adding sodium chloride and potassium carbonate to the food. Urine samples were collected every 24 h for determination of free dopamine and electrolyte excretions. The mean urinary phosphate excretion for 4 days of LPD was 0.17 +/- 0.11 mmol/day in the group with bilateral renal denervation and 0.18 +/- 0.11 mmol/day in the group with innervated kidneys. Likewise, dopamine excretion was similar in both groups in the absence (2.5 +/- 0.2 microgram/day) and in the presence (2.3 +/- 0.1 microgram/day) of the renal nerves in rats fed LPD. Increasing dietary phosphate intake from 0.07 to 1.8% significantly increased urinary phosphate and dopamine excretions. The mean urinary phosphate excretion for 4 days was similar in the denervated (4.4 +/- 0.9 mmol/day) and innervated (4.1 +/- 0.5 mmol/day) groups. The mean urinary dopamine excretion for the 4 days of HPD significantly increased to 4.5 +/- 0.5 microgram/day in the group with chronic bilateral renal denervation and 3.7 +/- 0.2 microgram/day in the group with innervated kidneys. Plasma 3,4-dihydroxyphenylalanine (DOPA) and dopamine levels were not changed by increased dietary phosphate intake. (ABSTRACT TRUNCATED AT 250 WORDS)
authors: Department of Physiology and Biophysics, Mayo Clinic and Foundation, Rochester, Minn.
authors: T J
authors: TJ
authors: Berndt
authors: A A
authors: AA
authors: Khraibi
authors: V
authors: V
authors: Thothathri
authors: T P
authors: TP
authors: Dousa
authors: G M
authors: GM
authors: Tyce
authors: F G
authors: FG
authors: Knox
mesh_terms: D000818:Animals; D003714:Denervation; D004032:Diet; D004298:Dopamine / Q000652:urine*; D007668:Kidney / Q000294:innervation* / Q000378:metabolism; D010710:Phosphates / Q000008:administration & dosage* / Q000652:urine; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D010710:Phosphates; D004298:Dopamine