title: Effects of citrate on urinary calcium excretion.
abstract: Thyroparathyroidectomized rats were studied during control, citrate infusion, and recovery periods to analyze the effects of citrate on urinary calcium excretion. The rats were infused with human PTH-(1-34) at a constant rate throughout the experiments that produced physiologic circulating PTH activity. Ultrafiltrable calcium was measured with a micropartition system while maintaining constant the pH and PCO2 of the sample. The plasma acid-base status, filtered load of calcium, and urinary sodium excretion rate did not vary during citrate infusion. The urinary calcium excretion rate increased from 71 +/- 9 nmol/min/g kidney during control period to 122 +/- 22 nmol/min/g kidney (p less than 0.05) during citrate infusion, and then returned below control levels during recovery period. A strong positive linear relationship was observed between the urinary excretion rates of calcium and citrate (r = 0.88; p less than 0.001). We conclude that tubular fluid citrate inhibits renal calcium reabsorption probably by forming calcium-citrate complexes.
authors.affiliation: Laboratoire de Physiologie, Université Paris 6, Hôpital Broussais, Paris, France.
authors.forename: P
authors.initials: P
authors.lastname: Borensztein
authors.forename: P
authors.initials: P
authors.lastname: Patron
authors.forename: M
authors.initials: M
authors.lastname: Bichara
authors.forename: J P
authors.initials: JP
authors.lastname: Gardin
authors.forename: M
authors.initials: M
authors.lastname: Paillard
mesh_terms: D000818:Animals; D002118:Calcium / Q000008:administration & dosage / Q000097:blood / Q000652:urine*; D002951:Citrates / Q000097:blood / Q000494:pharmacology* / Q000652:urine; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008657:Metabolic Clearance Rate; D010281:Parathyroid Hormone / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000493:pharmacokinetics / Q000652:urine
chemical_list: D002951:Citrates; D010281:Parathyroid Hormone; D012964:Sodium; D002118:Calcium