scholarly journals Erythrocyte Ascorbate Is a Potential Indicator of Steady-State Plasma Ascorbate Concentrations in Healthy Non-Fasting Individuals

Nutrients ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 418 ◽  
Author(s):  
Juliet M. Pullar ◽  
Susannah Dunham ◽  
Gabi U. Dachs ◽  
Margreet C. M. Vissers ◽  
Anitra C. Carr

Plasma vitamin C concentrations fluctuate in response to recent dietary intake; therefore levels are typically determined in the fasting state. Erythrocyte ascorbate concentrations have been shown to be similar to plasma levels, but little is known about the kinetics of ascorbate accumulation in these cells. In this study, we investigated ascorbate uptake into erythrocytes after dietary supplementation with vitamin C and compared it to changes in plasma ascorbate concentrations. Seven individuals with baseline fasting plasma vitamin C concentrations ≥ 50 µmol/L were depleted of vitamin C-containing foods and drinks for one week, and then supplemented with 250 mg vitamin C/day in addition to resuming their normal diet. Fasting or steady-state plasma ascorbate concentrations declined to almost half of their baseline concentration over the week of vitamin C depletion, and then returned to saturation within two days of beginning supplementation. Erythrocyte ascorbate concentrations exhibited a very similar profile to plasma levels, with values ~76% of plasma, and a strong linear correlation (r = 0.89, p < 0.0001). Using a pharmacokinetic study design in six individuals with baseline fasting plasma vitamin C concentrations ≥50 µmol/L, we also showed that, unlike plasma, which peaked between 2 and 4 h following ingestion of 200 mg of vitamin C, erythrocyte ascorbate concentrations did not change in the six hours after supplementation. The data from these two intervention studies indicate that erythrocyte ascorbate concentration provides a stable measure of steady-state plasma ascorbate status and could be used to monitor ascorbate status in healthy non-fasting individuals.

1989 ◽  
Vol 37 (2) ◽  
pp. 185-189 ◽  
Author(s):  
L. v. Bortel ◽  
R. Böhm ◽  
J. Mooij ◽  
P. Schiffers ◽  
K. H. Rahn

Nephron ◽  
1989 ◽  
Vol 53 (1) ◽  
pp. 18-23 ◽  
Author(s):  
Susan H. Carchman ◽  
Domenic A. Sica ◽  
Judith Davis ◽  
James T. Crowe Jr. ◽  
Albert J. Wasserman ◽  
...  

2001 ◽  
Vol 62 (10) ◽  
pp. 812-817 ◽  
Author(s):  
Hsien-Yuan Lane ◽  
Michael W. Jann ◽  
Yue-Cune Chang ◽  
Chih-Chiang Chiu ◽  
Ming-Chyi Huang ◽  
...  

1984 ◽  
Vol 144 (6) ◽  
pp. 625-629 ◽  
Author(s):  
R. G. McCreadie ◽  
Margaret Mackie ◽  
David H. Wiles ◽  
Aksel Jorgensen ◽  
Villy Hansen ◽  
...  

SummaryEleven male chronic schizophrenics were given, serially, oral pimozide, fluphenazine, and flupenthixol; the two latter were also given intramuscularly as decanoates in oil. Oral haloperidol was given before and after each drug. Analysis of variance of steady state plasma levels of the different neuroleptics showed considerable within-individual variation in such levels, probably due to differences in absorption and metabolism and between routes of administration. The findings suggest that if a patient fails to respond to one neuroleptic, there may be good pharmacokinetic reasons for switching him to another belonging to a different group, or for giving the same neuroleptic by a different route of administration. The study also showed that previous administration of one neurololeptic may influence the steady state level of another. The various neuroleptics produced different effects on plasma prolactin levels.


2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Yazhou Li ◽  
Kelli L. Vaughan ◽  
David Tweedie ◽  
Jin Jung ◽  
Hee Kyung Kim ◽  
...  

AbstractThe time-dependent (30 min - day 84) plasma profile of PT320, a sustained-release (SR)-Exenatide formulation under clinical development for treatment of neurodegenerative disorders, was evaluated in nonhuman primates after a single subcutaneous dose and was compared to Bydureon. Exenatide release from PT320 exhibited a triphasic pharmacokinetic profile. An initial peak occurred at 3 hr post-administration, a secondary peak at 5 days, and achievement of Exenatide steady-state plasma levels from day 10–28. Systemic exposure increased across PT320 doses, and Exenatide levels were maintained above the therapeutic threshold prior to achieving a steady-state. In contrast, Exenatide release from Bydureon exhibited a biphasic profile, with an initial plasma peak at 3 hr, followed by a rapid decline to a sub-therapeutic concentration, and a gradual elevation to provide a steady-state from day 35–49. Exenatide total exposure, evaluated from the area under the time-dependent Exenatide concentration curve, was similar for equivalent doses of PT320 and Bydureon. The former, however, reached and maintained steady-state plasma Exenatide levels more rapidly, without dipping to a sub-therapeutic concentration. Both SR-Exenatide formulations proved well-tolerated and, following a well-regulated initial release burst, generated steady-state plasma levels of Exenatide, but with PT320 producing continuous therapeutic Exenatide levels and more rapidly reaching a steady-state.


2007 ◽  
Vol 21 (5) ◽  
Author(s):  
Leah Cahill ◽  
Bénédicte Fontaine‐Bisson ◽  
Ahmed El‐Sohemy

Epilepsia ◽  
1984 ◽  
Vol 25 (4) ◽  
pp. 476-481 ◽  
Author(s):  
Roberto Riva ◽  
Fiorenzo Albani ◽  
Giovanni Ambrosetto ◽  
Manuela Contin ◽  
Pietro Cortelli ◽  
...  

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