title: Important aspects of urine sampling for angiotensinogen measurement: time and preservation conditions in healthy individuals.
abstract: Intrarenal renin-angiotensin system (RAS) plays an important role for the pathogenesis of renal injuries.  Experimental studies have demonstrated that angiotensinogen levels in renal tissues reflect the activity of intrarenal RAS.  However, dynamics of urinary angiotensinogen have not been investigated in detail.  Therefore, we examined the preservation conditions of the measured values of urinary angiotensinogen concentrations and an ultradian rhythm of urinary angiotensinogen excretion in humans.  Urine samples were collected from 24 healthy volunteers.  The urinary concentrations of angiotensinogen were measured by using ELISA.  Two different urine preservation conditions were examined.  One cycle of freeze-and-thaw did not change the measured values of urinary angiotensinogen concentrations.  Moreover, to keep urine samples at room temperature for 12 hours did not change the measured values of urinary angiotensinogen concentrations.  Thus, preservation conditions do not change the measured values of urinary angiotensinogen concentrations.  Regarding an ultradian rhythm, blood pressure and the urinary concentrations of angiotensinogen were measured at 09:00, 13:00, and 16:00.  The averaged levels of blood pressure were similar over the time.  The average of urinary angiotensinogen/creatinine (Cr) ratios was 8.73 ± 1.15 ng/mg Cr at 09:00, 9.53 ± 1.58 ng/mg Cr at 13:00, and 8.58 ± 1.26 ng/mg Cr at 16:00.  The urinary angiotensinogen excretion in healthy volunteers does not have an ultradian change during the daytime (P = 0.482).  This may be another indication that the intrarenal RAS is independent of the systemic RAS.  We have to pay attention to these findings in handling urine samples for measurements of angiotensinogen.
authors.affiliation: Department of Cardio Renal and Cerebro Vascular Medicine, Faculty of Medicine, Kagawa University, Kagawa, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Nishijima
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kobori
authors.forename: Tadashi
authors.initials: T
authors.lastname: Sofue
authors.forename: Kumiko
authors.initials: K
authors.lastname: Kaifu
authors.forename: Kumiko
authors.initials: K
authors.lastname: Moriwaki
authors.forename: Taiga
authors.initials: T
authors.lastname: Hara
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Hitomi
authors.forename: Masakazu
authors.initials: M
authors.lastname: Kohno
authors.forename: Akira
authors.initials: A
authors.lastname: Nishiyama
mesh_terms: D000204:Activity Cycles / Q000502:physiology; D000808:Angiotensinogen / Q000652:urine*; D001794:Blood Pressure; D003404:Creatinine / Q000652:urine; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D012084:Renin-Angiotensin System / Q000502:physiology*; D013048:Specimen Handling / Q000379:methods*; D013696:Temperature; D016482:Urinalysis / Q000379:methods*
chemical_list: D000808:Angiotensinogen; D003404:Creatinine