title: Circadian rhythm of glomerular filtration rate in normal individuals.
abstract: 1. In a group of 11 normal individuals we measured glomerular filtration rate (GFR) by inulin clearances and effective renal plasma flow (ERPF) by p-aminohippurate clearances during a period of 24 h and a regimen of bedrest, identical food intake per 3 h and normal sleep/wake and light/dark cycles. 2. All subjects had a circadian rhythm for GFR with a maximum of 122 ml/min (SD 22) in the daytime, a minimum of 86 ml/min (SD 12) at night and with a relative amplitude of 33% (SD 15). 3. ERPF had a circadian rhythm with a similar relative amplitude as the GFR rhythm, but with a different phase. Because of this difference in phase, the calculated filtration fraction (GFR/ERPF) followed a circadian rhythm as well. 4. The circadian rhythms of urine volume and sodium excretion were in phase with the GFR rhythm, but the potassium rhythm had a different phase, probably because urinary potassium is largely derived from tubular secretion. 5. Urinary albumin and beta 2-microglobulin excretion had a circadian rhythm in phase with the GFR rhythm. 6. The highest quantity of sodium, water and beta 2-microglobulin was reabsorbed in the daytime; tubular reabsorption, expressed as percentage of the filtered load (fractional reabsorption), had a rhythm with a reversed phase.
authors.affiliation: Department of Medicine, Academic Medical Centre, Amsterdam, The Netherlands.
authors.forename: M G
authors.initials: MG
authors.lastname: Koopman
authors.forename: G C
authors.initials: GC
authors.lastname: Koomen
authors.forename: R T
authors.initials: RT
authors.lastname: Krediet
authors.forename: E A
authors.initials: EA
authors.lastname: de Moor
authors.forename: F J
authors.initials: FJ
authors.lastname: Hoek
authors.forename: L
authors.initials: L
authors.lastname: Arisz
mesh_terms: D000328:Adult; D000419:Albuminuria; D002940:Circadian Rhythm; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male; D011188:Potassium / Q000378:metabolism; D012079:Renal Circulation; D012709:Serum Albumin / Q000032:analysis; D012964:Sodium; D014556:Urine; D001613:beta 2-Microglobulin / Q000652:urine
chemical_list: D012709:Serum Albumin; D001613:beta 2-Microglobulin; D012964:Sodium; D011188:Potassium